Sorry you are in a bad situation.
I imagine that it says in your purchase agreement that taxes will be prorated as of the date of close. The bank IS paying the back taxes. You are to pay the portion of the taxes only for the period that you will own the home. Since taxes are paid in advance in Michigan, the buyer almost always has some tax money to pay at close. It sounds like this might not have been explained clearly to you.
The only other closing costs I can think of might be recording fees (like $20) and possibly a closing fee from the title company. If that fee is high, see if you can negotiate it down.
Is your agent also the listing agent or do you have your own buyer's agent?