I'm a WHM, and I put my stat points in Vitality over Mind specifically for PvP. I also use two ilvl 100 tank pieces on my right side. As a healer, you're at the top of the priority list in most PvP formats so being able to take that random bit of burst damage is important, and not having to worry about constantly healing yourself because you only have 3.5k HP is nice as well. Damage packets in PvP are much smaller than they are in PvE ( not including Limit Breaks ). A Cure1 that heals for 900-1k is generally enough to keep people alive fairly easily unless they're getting focused heavily by a group of people in which case a Benediction may be in order or, Cure2 provided you have time and in some cases, it may be best to just let them die and rez them safely at your location while dispersing that concentrated DPS. < Huge run-on sentence, I know.

For your second question, you can turn those Paladin Hotbars off, and move a few more Hotbars to the same location as your Paladin ones. Then, when you need to switch to the Paladin bars, just turn your healing bars off. This can be done under Character Configuration ( Hotbars ), and HUD layout. It's what I do at least.

Good luck.