1. Generally you should only use things that you either own, or could reasonably access. For instance, i could use in my RP a pinhook starfighter, because i could theoretically have one or already do. an X-wing however,unless you are in the NR, is not nearly as likley, so id steer clear of it.
2. Many,Many people do that.
3. There are a few people who have npc charachters that they use in their RP's. friends, family,slaves,things like that. I'd imagine the same rules apply to small creatures, but again, be realistic. You may have an Elix that rides on your shoulders, but you can't take a pet rancor into a bar, even if it is named cuddles.
Anyone,correct me if i'm wrong, but that's my observations as far as RP is concerned.
As far as I am concerned, a blaster is a blaster, pretty much. If you're using something that's not on the list, simply add an OOC note that people can treat it as something on the list (for example a GZ-32 heavy blaster pistol could be treated as a DL-44) and you're good to go. Something like the sonic blaster might be a little more tricky due to the effects, but generally if you assume it's comparable to something we do have (that the public has access to) then you won't have an issue.
"May the Grace of Ara go with you, and His Vengeance be wrought upon your enemies."