Garmin says the training effect is based on the rider's history. The same ride could score differently for a new rider over one that's been training a lot. The range is 0 to 5.
Garmin's ride recording should show time for each heart rate zone, that can be helpful. Your average heart rate sounds good to me--3 hour rides will have some easy pedaling or coasting mixed in, to lower the average a bit. 55 to 65 feet per mile is good--I have those kind of hills on my rides, and it's a good mix of climbing, flats, and descending.

Your week sounds good to me. Perhaps, substitute a short ride with some all-out hard efforts for one of your weekday rides, once a week or every other week. That would be informal intervals.