I want to make sure I understand your current 13-club set-up.
RAC = 2i through PW (9 Clubs)
Driver and two Fairway Woods (3 clubs)
A couple of things you could do: drop a FW, and add two more wedges.
You could add 52* and 56*, or 52* and 58*
If you really wanted to add three more wedges, you might drop a FW and the 2i.
FYI, four wedges ( PW + 3 new) can be a whole lot harder to manage than three wedges.
For starters, you might ask a friend to try out a 60* LW and see if you can hit it. Many golfers have trouble with it, and it takes a lot of practice because the ball goes so high. Or, you could buy a used 60* and try it out, and turn it in for store credit if it doesn't work.
Or, you might get a 58*, kind of a combo LW and SW. Many of the pro golfers have a 58* as their most lofted wedge.
You want the distance gap between wedges to be fairly equal, so you can plan your partial shots better.
Depends on what you really want from your wedges. I carry four (46* PW, 52* GW, 56* SW and 60* LW). One of my regular playing partners carries only two wedges (45* PW and 55* SW). Most people I play with carry three wedges. The friend with only two wedges doesn't give up anything to the rest of us because he can extract anything he needs from those two clubs. He compensates for the lack of a GW by hitting lower punchier shots with his SW or choking down on his PW.
I'd definitely add a 55* or 56* SW and after that probably a 60* LW. Without knowing anything about your game, I'd drop the 2i to compensate.
You said you carry 3 woods... Does that include your driver? Or do you mean that you carry 3 fairway woods, i.e. 3-5-7?
Regardless, it seems like any woods 5 and lower wouldn't make much sense in your bag, especially if you feel like you hit your long irons well. A 2i is lofted like a 3w, and a 3i is lofted like a 5w. Yes, the clubs are shorter, but loft makes more difference than club length when it comes to overall shot distance.
Anyway, wedges are super awesome , and getting at least two is certainly a good idea. I carry three (52, 56, 60), and they all have important functions. They certainly see a lot more action than my 3-wood. (sigh... my 3-wood)
Degrees is all up to you. Frankly, I'd start by picking from the "standard" lofts of 52, 56, 60, and go from there. Remember, clubs can be bent if you're really that picky about lofts. Brand is also up to you. Just like anything else in your bag, gotta try before you buy, right?
Hope this helps.