[Can a model have more than one property?]

No, but it has been put forward as a possible feature for the future.

[How to make an SRB ignite one detached.]

IIRC it's not supported yet. It's not just a matter of editing the cfg.

Actually, now it is, although I don't think anyone's made use of it yet.

According to the readme file;

* Parts now have an ActivatesEvenIfDisconnected parameter on the cfg to allow them to be activated after jettisoning

[[Concept] The Mun]

They did have a moon in an early alpha build, but at that point the game wasn't even in 3D, so it's hardly going to be an easy thing to put back in.