feel your pain on the saddle issue, I’ve switched to a Fizik aliante open ( you can do a test to check your spine angle) and it helped a bit but 40 minutes in start feeling it , getting out the saddle for a few seconds gets the blood flowing again.
I’m half way through week 4 on mid level SS base & looking forward to the end, too stubborn to drop any rides now though with only one high TSS ride left. Thinking I’ll drop back to low intensity for SS Level 2 next & maybe add an extra easy ride each week.