It actually doesn’t sound too bad to me. While the normal procedure would be to let him get used to his new home for a few weeks, then do prebonding, I suppose you could do prebonding while he gets used to his new home. I do think you rushed the bunny dates a bit… but it still doesn’t sound all that bad. Since you’v already introduced them, I’d probably keep doing the prebonding for a few weeks, swapping toys, litter boxes, etc and find a much more neutral area. The fact that he is marking in the neutral area means he hasn’t claimed a home base yet that is distinct from the area you labeled “neutral”. He is taking a much larger area as his home base. This will not be good for bonding. So I’d take a few steps back, let him realize which area is his, so that you can have a truly neutral area for the bunny dates. But let them continue to be able to see each other – just hold off on physical contact for a few weeks. It sounds like you will still have an easy-ish bond.

I woudln’t do the car or bathtub just yet – but those are good options for when you are ready to do bunny dates. Typically, I would say – let him get used to what is his and not his. I.e., wait a few weeks before swapping stuff. Only reason I might do the swapping now, is that you have already somewhat introduced them to eachother. Not sure what other’s think of this. If you are unsure, don’t swap stuff, give him a few weeks to figure out what belongs to him. That’s the most common way of doing it. For seeing eachother – no closer than 6 inches through their cages. No play dates. No meetings. Allow them to live within sight of eachother. If he is acting up, posturing, showing his tail/ears at her, separate their cages until he stops acting up. As he calms down, you can bring their cage closer. I got to where my unbonded rabbits can share a NIC cube fence. The idea of swapping is to introduce her scent into his territory as a matter-of-fact. But he needs to establish a territory first – and it can’t be your whole entire abode! I’m also limited on what is left that is truly neutral. On occasion, I have used a friend’s house, and even hotels while I go on travel.
How quickly to move really depends on the bunny. You could skip the swapping for a few weeks to allow him to fully realize what is his, you could keep them completely separate for the first few weeks, or as long as he is not acting up, you could house them in the same room with some distance. After a few weeks, you could start the swapping. Then once his territorial behavior subsides – start the bunny dates (car/bathtub).

For neutral space if you have extra pens and a backyard, I took my bunnies outside on nice days and they seemed to agree it was pretty neutral even if my male was sometimes outside before, since rain and wind and other things affect the scents unless your bun is out all the time

Of course this doesn’t work if you have too many wild animals in your area or too hot or cold of a climate or no backyard or something.

Maybe give your bathroom a scrub with some vinigar if your first bun has already been in there? Vinigar usually cancels out bunny smells. A bonus is the usually slippery tiles in bathrooms makes it more unlikely for them to fight

I thought you were going to do more pre-bonding??? 

If she isn’t settled in yet, and you date them in his space, you risk them bonding weakly, due to her not being completely confident. Then their bond could break later if she decides that she is no longer happy with their terms. I speak from experience here, please listen to the advice you were given by Vanessa. 

That said, the sessions aren’t going terribly, so it sounds like ONCE you do prebonding, the actual bonding will probably go smoothly. 

Bunnies tend to get very territorial over their litterbox, so it’s good that they shared it, but I would probably remove it for future dates, until you are at the point where they are spending several hours together without scuffling. 

Ignoring is good, eating together is good. 

You must stop circling, and do not allow reverse mounting. And you must not date in his space. 

What happened to giving him time to settle???