How to prove innocent of forgery?

I was office manager for small business for 18 months. Me and owner were having an affair and when things went south threats were made and I am now being accused of forgery. I was authorized by him to sign his name to checks. EVERY check that went out of that office was signed by myself not him. To vendors, bank loans, payroll everything. I at the end of the month would do reconciliation and pay back shareholder (him) and myself for expenses accrued throughout month for things such as office supplies, postage, permits for building inspectors etc all purchased by me through my credit card or with cash. OR the checks were to pay me the rest of my pay every week which was half legit for audit purposes and half cash as he wanted to limit his payroll tax payments as much as possible. We went over bank statements every week and he was well aware of the checks I wrote to myself. He never added me as a signer or gave me power of attorney. I just signed. He is now saying all checks to myself are forgeries however other ones to vendors etc are legit. How can those checks to myself be forgeries yet rest is legit? Technically then every check I ever signed is forged. This man is in deep financial trouble and was using the "get you before you get me" mentality. Now he waits until a month after to file a report and an affidavit of forgery. I have SEVERAL witnesses that can attest to the fact that I had verbal authorization including the CPA and other technicians that worked there. I have some reciepts for office supplies and the building inspectors can say I paid for the permits. Also other employees were getting cash compensation as well in forms of checks. I need to know how bad this may be for me. My bank is refusing to reimburse his bank and saying they dont believe his story as plausible. Not sure about his bank yet. However do i have recourse for him lying and possibly costing me monies with my other bank where they are holding me accountable for a $300 check as "forgery/breech of warranty" I did nothing wrong other then my job and trust him. How far criminally is this likely to go?