I will be flying United IAD-MUC on one ticket, then flying Air Berlin MUC-TXL on a separate ticket. How much time should I allow taking into account immigration/customs and/or baggage? I will just have a typical roller board carry-on suitcase and a briefcase. I will be arriving at 7:50 am. Will I be able to make a 10:40 am flight?

On the return, I will be on a Lufthansa flight LEJ-MUC on one ticket and MUC-IAD on United on a separate ticket. Not sure if they will make me check my bag, but if so, if I arrive in MUC at 10:30 am will I be able to make a 12:20 pm flight?