Id suggest 124 grain speer gold dot for self defense. For rnage time, get cheaper fmj/ball ammo, remington umc works well for me and is generally a good price. 147 grain ammo tends to jam in autos.

That depend if the pistol is rated for +p or +p+. If the pistol is rated for +p+ it will fire any 9mm ammo (9x19). If the pistol isn't rated to fire +p, you are limit to ammo below +p.

I am not sure if the XD is rated for +p+. I'm not a big fan of XD and the only plastic pistol that I think worth the money are Glocks.

I suggest you go to a gun show or gun range (rent) to get a feeling on the pistols that you want to buy.