Those first two weeks were absolutely perfect! Those weeks were dialed in and your efforts were great! Your first set of 3 minute Vo2 max efforts on July 29th you started a bit easy but after that the rest of your efforts that day the previous week for 4 minutes were great! You moved from the lower zone 5 to the middle end of the zone even with the longer 4 minute efforts. So feel free to push those a bit more if you are feeling good the next go around.
Your last group ride on August 8th, the Gap ride, was an awesome ride! Big amount of sweet spot / threshold efforts. You did 269 TSS in 3 hours. That is 70 TSS more than the previous week in the same amount of time! Shows how much more of an effort that ride took. You actually hit your peak 1 hour power on this ride and that was after 2 hours of hard riding! So that is impressive especially considering the day started off with a 20 minute climb that you did over your FTP! So you still had good endurance to ride that strong later on in the ride. Great sign of fitness.
The first group ride was good. Not quite the intensity of the gap ride, but still not bad. You did get in 202 TSS for the 3.5 hours so that is a solid pace. Nearly 60 TSS per hour which is kind of what you want as the minimum for a sweet spot group ride. The plan called for 175 TSS but since you rode a little longer you went over that target so in the long run you did get in the proper workload.
The sweet spot intervals you have been doing are perfect! 91% of your FTP so right in the middle to upper end of sweet spot which is a great pace! Not too easy and not too hard which is allowing you to repeat those efforts consistently. That is what you really want.
As for shorter trainer rides on Sunday you can do that. What you want to look at is TSS. TSS is your training stress score. This is how hard a ride is. If you ride more zone 3 as opposed to zone 2 power you can accumulate more TSS in a shorter period of time. We recommend this a lot with our riders who have to ride the trainer. Just trying to cut the trainer time. There is a caveat to this however. With the Sweet spot 4 plan the idea is to keep the intensity down on days you are not doing efforts. This way you are fresher when its time to go hard. Will doing 1.5 - 2 hour ride with some tempo burn you out, not but be careful with how hard you ride.
So for a 2 hour zone 2 heart rate ride you have been getting in 95 TSS. So basically 43 TSS per hour. So that is what your goal should be.
Make sure to get that ride in on next Tuesday before the intervals on Wednesday. You will want to open back up after a few days off. That first set maybe more of a warm up than anything so don’t worry too much about the outcome of the power. It maybe a shock to the system, but will be more opened up after that.