Packers fans are not allowed to ask for help on this board.

Provided you're on time (which the AB flight usually is), 75 minutes is plenty of time. TXL is a tiny airport that was scheduled to close years ago, so walking from gate A0 or A1, where you're likely to arrive, to the C gates, where you're likely to depart, will take 10-15 minutes tops. Unlike most airports, each gate at TXL has its own immigration facilities, so it can get a bit backed up on the jetbridge waiting to get off. Just make sure you're in the line for non-EU citizens and you'll be fine. They'll ask a couple of questions about how long you're staying and what the purpose of your visit is, and might ask for your connecting boarding pass, so make sure to have that handy.

As offerendum mentioned, you should be able to have your bags checked all the way to Munich from Chicago. If you're able, I would carry on the bags instead of check, as TXL is notorious for being worst than most when it comes to baggage during busy periods. If not, don't sweat it too much.

I would familiarize yourself with other TXL-MUC flights in case your flight is delayed from ORD. There are multiple daily flights, so even if you do miss the connection, they should be able to rebook you on another, such as the 10:40 flight, which has plenty of open seats.

Bottom line: don't stress out about it too much; enjoy the experience!