Can GC alter my Change Order, submit to Government Entity, then add his markup on misrepresented numbers?

Backstory: In early 2020 we were approached about doing the Electrical portion for a New Construction Maintenance Facility County Project in Texas. The GC had already received Electrical Bids from other Contractors (so he said), and since we were doing another similar project for GC asked if we could do job for $xx,xxx amount? We told him we had to see plans and do take off, cost analysis, etc. GC tried to press Owner/Master Electrician to commit to cost saying that it would be an easy job, but we insisted on seeing plans before committing to anything. When I got copy of plans I immediately noticed issues. Sheets were missing that contained the One Line Information (Electrical Service Size, Type, Etc.), as well as the Service Site Information which gives details for the Underground Service (Conduit, route, distance, etc.). I informed GC that I needed these sheets before I could give accurate cost analysis, but while he is getting them I will do the Take off on Gear & Lighting. The next day when I submitted Schedules for The Gear & Lighting to the appropriate vendors, I was contacted back by three separate vendors saying that we did not have the correct plans for this project, the ones I submitted were rejected, and had been updated with new plans. I immediately informed the GC of this claim, and submitted an RFI stating we needed correct plans, as well as missing sheets with One Line. After about 3 weeks of multiple requests, the GC informed me that these are the plans we are to use, and ONLY these plans. I relayed to my Lighting Vendor the directions, received my Quotes from them, crunched the numbers, without the specs for Site Service & Meter, and submitted Estimate which included only Interior Power and Lighting from the sheets I had. We were informed the the Service Design was having to be redesigned by Power Company, and once approved, we would be provided to issue a Change Order request. After submitting my Estimate to GC, he asked if I could sharpen my pencil a little, dropping about $3,000 in Estimate? He also made the comment that if needed, I may be able to make a little back from the Exterior Site & Service Change Order that would be submitted when plans became available. I looked it over and agreed, bringing it down to below the figure he had in mind. Contracts issued, signed and returned, material submittals completed, and then the wait. Six months later, every Sub Contract receives a group email informing us that we all had been using the wrong plans. We were given access to correct plans and the Electrical was still missing the One Line & Site Diagram for the Service. Fortunately, I did not need to alter my estimate since the Lighting Vendor had submitted cost for the correct plans that they had. I did need to change my count on a couple fixtures, but the count was lower, so really didn't affect anything for me. As work kicked off I made continual requests and reminders that we didn't have the design and layout for the Service, and this could potentially have dire consequences for the projected timeframe due to lead times needed to get Change Order Submitted and Approved, and I would not place orders for Materials until I knew we had approval. At the end of October 2020 we receive the One Line and Service Site Sheets. We are about 50% complete on the original Interior work. I prepared the Change Order Immediately using EBM (an Estimating Program) and National Averages built into the Program. The Change Order was higher than the original Estimate (original$50k, change order $65k), since Change Order had over 330' of Trenching, multiple runs of 4" Schedule 80 Conduit totaling over 650', #500 CU Wire totaling 330', and #4/0 CU Wire totaling over 720'. Change Order Submitted to GC on 11/3/2020. After a few more changes made by Architect, I submitted the final Change Order on 11/18/2020. Sometime after that we were informed that it had been submitted and was under review. On December 15, 2020 we were informed the Change Order had been approved and was asked to get materials ordered. I informed the GC that I would need some form of acceptance of Change Order, even if it had to be a Letter of Intent before I could place the orders. During this time there was some talk with Master Electrician/Owner about some of the work on Change Order should have been included in the Original Estimate. I was not included on these conversations, even though I am the Sole Estimator, and only person that worked on the Estimate. The ME/Owner got GC on phone and conferenced me into the call. I reinforced that I did not include any work that pertained beyond the canopy of the building because I did not have Plans which specified the design of service, size, or route. I did not know the length of service conductors from Transformer to Panel inside the building, so therefore could not provide accurate cost. I was told that there was a sheet which showed potential routing of Utilities (Water, Sewer, & Electrical) in the Civil Drawings section, so I should of included at least part of the Trenching and PVC Conduit in original bid. I told them that I had informed them over and over that I could not provide cost without the One Line & Electrical Site Plan, and the Civil Drawings were not detailed nor accurate to existing conditions when doing the walk through. My Change Order included Scope Of Work which explicitly detailed the Trenching & Conduit in the work. On 01/21/2021 we were informed that the Change Order was Issued to GC. The same day I received Contract for Change Order in the amount of my Estimate. 4 hours later I received another email stating that the first Contract for Change Order was Voided, and a new Change Order Issued with a $15,452.18 deduction for scope not required. The contention is that since Civil Drawings had an approximate routing of utilities, I should have included in my Original Lump Sum Bid. Therefore, they were taking my itemized Change Order, applying my cost formula per square foot to the Lump Sum Bid, and deducting that as a charge back. After multiple emails disputing there claims, they are know having no communication with me, and pressuring the ME/Owner to sign the Contract. Now, if you are still tracking with me, here is the kicker! Through Open Records available I have discovered that GC Altered my Change Order before submitting to County. He raised my costing from $65,299.24 to $83,325.04, an increase of $18,025.80, then applied the Contracted Allowable Markup for the GC when submitting Change Orders in the amount of $9,585.79, for a total increase of $27,611.59 above my Change Order Amount. Then, if you add in the amount of the deduction which they are trying to impose, the Gross Profit the GC is trying to gain off my $65,299.24 cost is $40,899.37. Main Question--Is it legal for the GC to take my Change Order Estimate, alter the cost, submit it as if it is my cost to the County, then pocket the difference? Thank you!