That breaker is only 50 amps so it may trip on pump startup if you kick all pumps on at the same time. Just turn each pump on separately, not all at once. I've used that fuse box before, since you already have the power terminal I'd just use it and return the fuse panel. Save yourself some work, also you may want to use breakers instead of fuses. They don't fit in that fuse box. I have these, they reset automatically.

https://www.amazon.com/Bussmann-CB22...2Bbreaker&th=1