Also, I feel like I've been the big bad guy of doom lately on this forum

I really am pulling for you. When I list all the things you need to think about doing, and all the problems that may arise, it isn't to discourage you, its just because I want you to be as prepared as possible to tackle the next challenge.

Think of my tone of voice as the likeable coach from the movies thats pushing the kids for their own good

Really though, as much as I know the news must suck for you that giving her seahorse tankmates will be rough, if not impossible, you are getting the opportunity to nurse this seahorse back to health, and possibly be one of the only people to be keeping this species successfully at the moment.

And there are plenty of fun fishy tankmates and corals that are seahorse safe that you can add down the road. You can even set up ANOTHER seahorse tank next to it! And ANOTHER, and ANOTHER... so many species, so many excuses to set up a new aquarium
And if the worst happens, and she doesn't make it. You can sell off your LR, etc. to someone who doesn't keep SH, sterilize the tank, and set it up brand new.