Good luck with trying tunnels and other things! There are lots of DIY ideas online and YouTube.
That’s a tough one, the reason I got 2 was because after reading so much about how they are happier in pairs (when I got mine I had no idea how social they were), I felt determined to make it happen. If you’re living with parents they’d really need to be on board in my opinion, because you have to go through bonding and would need the help and support (and other neutral spaces in the house). So, as much as you can tell them about the benefits (if they can handle the work of the bonding process) would be best. Rabbits will spend most of the day with other bunny so you know they are less bored (and I don’t feel guilty if I’m gone a big part of the day), they are super cute cuddling each other ;), not much more expensive if you can start buying in bulk. There are higher vet bills though so there is a financial consideration. For me, it was most beneficial to use a specific rabbit rescue even though it was an hour and half away. They let you swap if one rabbit doesn’t work (or take it back without a swap), they already have the bun fixed and are more knowledgeable. So that was how I convinced myself at least.