What a coincidence. I have a Levo with a Zeb, X2 & Cascade link and now own a HSL as well (GX-AXS trim).
1) 4000' climbing in River might be possible. I picked up my HSL late last season so only got a few rides in. My weight is similar to you ~175lbs, and my longest ride in 6C temp was: 25.15km...