Sorry for the delay (Saturday night and all that).
Here's the botXXXXX XXXXXne. You could spend a small fortune to file a petition for a dissolution of partnership and to appoint a receiver, etc. Or, you could just walk into the bank tomorrow morning, open an new business account without your partner's name on it, transfer all of the working capital
into that account, notify your vendors
and/or creditors of the new account (assuming any make direct deposits or withdrawals.
And, then you meet with your partner and you say, "Time for full disclosure. Either you tell me exactly what's going on, and we straighten out everything right now, or we are done, and we can either negotiate a voluntary dissolution of the business, or you can sue me to recover your share of the business. Because from what I can see, you appear to be stealing from the business, and I'm not going to let that continue.
Also, you could hire a locksmith to change the locks on the doors that your partner has already changed, so that you can get to the business records.
Usually, the partner who starts playing games has sole control over the business accounts, and the leases, and he/she simply "fires" the other partner by refusing any access to anything. But, you're not in that circumstance. You can stop this thing dead in its tracks without spending any money on legal expenses. Yes, it's likely that you will have those expenses going forward. But, you may be able to shock your partner into "spilling his/her guts," and if you can, then maybe you can either save the business or end it in a reasonaby civil manner without a $50,000 lawsuit.
Hope this helps.