Cycling to work - 30 mile return
Even with an e-bike going to 150 miles a week is a big jump. Likely you just need to have a few rest days to allow your body to adapt and recover. 3 weeks is the range in where you start run into problem with long term recovery. 

I'd suggest switching down to 3 days a week until you feel completely recovered every day. Also lay off the strava, going for Personal Bests (PBs) is something you should keep to a minimum in daily rides. Focus on a pace that allows you to arrive at work w/o feeling stressed at all. This will help with the leg soreness/tiredness during the day. 

The saddle problem is a completely different one that every bike rider has to figure out. Some of it is just that you are spending a lot more time in the saddle, but most of it is finding the right saddle that works for you and your position on the bike. Unfortunately, there are no simple fixes. There are various saddle fitting guides out there, but nothing works for everybody and almost every saddle works for somebody. The best solution would be to find a local bike shop with a saddle demo program that will let you try different saddles until you find the one that works for you.