suggestions on extending tempo and sweet spot and FTP intervals are in this post:
and example TR workouts for sweet spot here:
Heaping on moar moar moar moar into a week is not the best strategy. Depending on your fitness level doing just 1 or 2 a week is all you need to see quick improvements. If you are really fit then maybe 3 a week. Just for kicks I cracked open the Time Crunched Cyclist and “experienced competitor road racing” has 3 hard days, 3 rest days, and a long Sunday endurance workout for ~7-8 hours a week. I’m just a lowly Cat 5 and made a pretty quick jump from 15 to 30 to 50 minutes, you might be surprised how fast you can work up the ladder and skip rungs. Good luck!