How often should this pen be mucked out?

Probably don’t remember me from a few weeks ago when I was on asking for help about a rabbit I caught in my back garden. Anyway I found the owner and they told me that they didn’t want it anymore and if we wanted to keep it that was ok.

So anyway, slowly but surely getting his wee house together. The pen is about 2 meters wide and 2.5 meters long. I’ve got some cardboard down then that’s 5 full bags of hay.

The cage in the back is his old house that he had to live in until this pen came. It was a loaner from the vets and is going back tomorrow.

Couple of questions?

1. This pen is in my garage. Does he need another house in the pen as well or will he be happy enough to just cut about the hay and sleep anywhere?
2. How often does it need mucked out? It’s pretty big and he’s pretty small so I was thinking swapping about 50% of the hay out per week
3. Any solutions to him knocking over his water dish constantly? I’ve got a sucky thing on the fence as well as a backup
4. Any other advice tips/toy suggestions are welcome.

The plan is to eventually get another 1 or 2 rabbits but not until I know how to introduce them etc.

Thanks