Bill,
Thx for numbering your questions. I like things organized like that 🙂
1. Dial back the load and allow your body to adapt. Don't go anywhere near your injury threshold. Be conservative. Make up the extra time, if you have any, with core training exercises, foam rolling and stretching.
2. Road riding is great. Match the intensity and duration of the ride that was intended to be off-road. Switching Sat and Sun beats riding the trainer or not getting the rides done. My view is that you can stay on plan and get a lot of fitness built on the trainer. It is a valuable tool, especially for Masters racers where training consistency is a cornerstone of fitness development. When the trainer is your best choice for a ride, shorten the warm-up and cool down time and keep the quality part of the ride in-tact. This works best for shorter rides. I don't recommend slogging out a 2+ hour on the trainer, especially if you have a fun outdoor option like cross-country skiing.
Lynda