My soon to be ex has a company which they just dissolved. I found out after separating that they had never filed taxes since the companies creation in 2006. It is a small side business. He had indicated when we were together there was an accountant and he told them it did not have to go through to our personal taxes. My problem is I have found out this was not done and incorrect. I have requested a 1065 and schedule k to file our final year and he is refusing saying he doesn't need to supply this. First of all I am wondering how much trouble he is in for never filing and if I have an alternative.

No idea, many part time side businesses never make money, and while the money in and out need to be accounted for, it may or may not be a issue at all.

In the divorce you can demand a full disclosure of all books for the business

I wish it was that easy lol... He and his partners all claim that one of the partners who left took all the books. It's a service based business which had no overhead so I know they made some money. He has tried lying about all of it even to the extent of saying he was an independent contractor is discovery for court. It's a mess and I am tired of dealing with it.

ALL divorces tend to be a mess.

Stick with it, because, by signing a JOINT return, you became liable for the income (and thus the income TAXES) associated with that company.