My husband can no longer run and I had never been able to run, haha. He can definitely walk and looks healthy. In a situation where we believe the connection is too tight or the walk is too long, we ask for assistance. There were times when we have sufficient connecting time but the walk was long, the cart or wheelchair would take us to a lounge near our gate or come back later to take us to the gate. As Orbitmic said, it's free. Go for it. You will enjoy your trip so much more.

Also, don't worry about flight delays. That's just part of traveling. If you miss connect in DOH and had to overnight, just enjoy the city. If you can get on a later flight with extra time, hopefully you have access to a lounge or just enjoy the airport. It is a very nice modern airport. And QR lounges are amazing. Take your time and enjoy whatever the day brings.

You should Definitely try FRA again with the assistance. Clearing immigration or security at some European airports with assistance is different at each airport. For some, it's like seeing the underbelly of the airport.