Well, I have a similar pump--Hayward 2spd Superpump with 1 hp full-rated and I run a 200lb sand filter with no trouble. It's not as simple as that--it's all about flow rates and feet of head and a lot of stuff I don't understand either. So rule of thumb goes.

I think for now you will be fine running on low 12 hrs a day-- it's still cheaper than 6 to 8 hours on full.

I've never heard of gluing in a spider gasket. Maybe it's a brand thing or the store guys are lost. If it looks like O-ring rubber, only as a spider web, I STILL think glue is a rotten idea.

I actually think you have something stuck in the multi-valve mechanism that's keeping it from closing the chambers properly. But that's a guess.