Can I write a stop work order for my portion of the job

The answer, as it is with many legal questions, is . . . it depends. In this case it depends on the language contained in your contract. 

Many contracts, including the AIA and Consensus Docs subcontract agreements, contain language that allows subcontractors like yourself to stop performing work on a project if the general contractor (GC) has not performed its duties regarding payment. You should review the contract or find an attorney who can help you review the language of the contract to see what you are able to do, since you haven't been paid. 

Additionally, as of now it sounds like you are out a significant sum of money. Rather than just providing lien notices, I would make sure you know your deadline to file a lien (75 days from the last date of work for most projects in Ohio) and make certain you get the lien recorded in the event you aren't paid. 

Further, to the extent you haven't been paid, but the GC has been paid for your work, you may have a claim against the GC not only for breach of contract, but also for violations of Ohio's Prompt Payment Act, which entitles subcontractors to 18% penalty interest on amounts withheld, as well as attorneys fees.