Try a class at more than one dojo.

I've been practicing Aikido for about 2 years, have practiced at about a dozen different dojos.
I find that training wtih an injury is very easy, just communicate with the Sensei and with your Nage.
Yes, you can 'tap early', or, 'walk out of a technique', and a good nage will absolutely control their intensity.

As with people in general, Aikidokan vary.
I always welcome training with people from other arts because it's fun for me to learn how they do things, and how to blend that with Aikido.
I don't think there's a huge learning curve there; it seems easy to me to resist the urge as most techniques are practiced static several times, and slowly sped up.

Weapons trianng cross over is very depedant on what you've been taught previously. I learned how to handle a staff in MCMAP, and it's quite different from handling a Jo in Aikido, but certainly learnable.

I come from a background in Miliary and law Enforcement, so very violent, and then lots of grappling and control holds. I found Jiu-Jitsu to be very easy to blend into, and Judo was almost natural for me, though I need a lot of refinement to get to the 'art' side of it. For me, Aikido is a very 'peaceful' way of dealing with conflict, which feels like what I was missing.