(Cross-posted.)
I am traveling with my 77 year old mother-in-law (and, an Indian 77 year old is physically much older than an American or European 77 year old!). Both of us are US citizens.

We were supposed to travel on June 1 from Miami as follows:
MIA-TXL-MUC-DOH-BLR.
The two tickets are business class awards, using AA miles.

When I found out last week that MIA-TXL is being canceled effective May 3, we asked for rebooking and as of now, are being rebooked as follows:
MIA-DUS-MUC-DOH-BLR

But while we had nearly 2 hours connecting time in TXL, we now have only 1 hour and 20 minutes connecting time at DUS.

Questions:
1. Is 80 minutes enough to connect at DUS, with a 77 year old lady who has limited mobility (can walk about 500 meters, slowly)?

2. Do we have go through immigration / customs / security again, or is it only transit security?

3. How good is wheelchair or other special services at DUS? (At FRA, we found it to be highly variable quality; sometimes good, at other times, we were left at many intermediate stops, sometimes for 30+ minutes waiting at an intermediate stop, never knowing when the next pickup will happen).

4. If, we find that we are lucky and have time, where would the better lounge be -- in DUS, or in MUC? And, what lounges can we access? (Unfortunately, the DUS-MUC is an all-economy flight.)

Thanks in advance for your help.