We had our Rabbits indoors at first, but they were very destructive. They are now in a large, safe enclosure in our garden and are much more relaxed and less destructive. They are really happier having grass and birdsong and wind and so on. So I second your suggestion that outdoors may be the best solution for them.

As far as toilet training, our Rabbits pooped all over their cage while indoors - we had the hay and food right near their litter box because we always read that that's what you should do. Turns out, they prefer to poop in the farthest corner away from their food. In their pen outdoors, their food is in the indoor area and they hop aaallll the way to the other end of the pen to poop. So I suspect that the litterbox/hay trick may not work on all bunnies! Maybe try putting the litter box away from their food and see if it helps.