Even though that indeed are quite a few assumptions, I agree they are quite likely to have happened.
When it comes to Bella entering his room, wouldn't you think she would've entered his room more often during the montage? I know that we don't see it, but the cat is out of the bag thanks to Nick so Tremolo and Bella don't really have a reason to hide it for them (unless they still hide it just in case a non-DIK is in the house, like tattletale Arieth).
Also, It's not unlikely that the picture isn't on the wall above his desk in canon, considering Jill has come more often to his room and seems to not have seen it (otherwise I'm pretty sure she would've recognized at least Miranda), plus we see other stuff on the same wall that I'm pretty sure aren't there (like the Pink Rose VIP card or his gym-card).