No Fiberglass tape needed;
Finish grinding the area of just the caulk seam all the way around the keel seam, make sure all the bad caulk is cleaned out. Before you re-fair and re-paint the rest of the grind spots you want to re-caulk that seam with 5200.
Pick a quart of Denatured Alcohol and clean rags. Use this to liberally clean the areas you have ground down. This also cleans epoxy off your hands and tools.
Use 2 inch wide painters tape to protect all the areas around just the caulk line. Put a nice thick bead of 5200 in the caulk line. Careful with this stuff, its nasty and sticky. have a couple 1 inch or so wide plastic putty knives to help get it where it needs to go. Only slightly overfill the area, no need to go crazy. Once this stuff is dry (and it takes several days) it can be sanded fair and painted over. You do not need to epoxy over it, but when you apply the fairing compound on the rest of the keel it wont hurt anything if some gets on there and ends up getting sanded.
You will probably only need one quart of epoxy and one can of fast cure hardener (I like West System because the pumps make mixing easy). You'll need one can of the 407 fairing filler.
When you brush on the first coat of un-thickened epoxy you don't have to leave it set to full cure and then wire brush it. Use a heat gun to accelerate the cure just don't boil it. When it is dry to the touch but you can still push your fingernail into it then you can mix up and apply the epoxy thickened with fairing filler. The strongest bond of epoxy to epoxy is a chemical bond, and you accomplish that by adding on the next coat before the first is fully cured and amine blush has not yet formed. Apply the fairing compound with a wide plastic knife and let cure overnight.
Now you can sand smooth with an orbital, start at 80 grit and get it close. I like to take a 120 grit sanding belt and cut it, then staple it to flat board to make my own long board. Finish out your shape... If you feathered your grinds, which it appears you did from the pics, match the level of fairing filler to the old fairing filler, which will still be lower than the old paint.
Use a quart size kit of Interprotect 2000 Epoxy Primer, only mix 1/2 can at a time. Apply with a 1/4" nap roller. It will be thick and have orange peel texture, don't worry about it! Let that dry until touch dry but you can still leave a fingerprint in it. Mix up the second half of the can and apply. You should be rolling over your faired repair area, the sanded 5200 seam, and slightly over the edge of the existing bottom paint edge around the repair. After the second coat let dry overnight.
Use your long sanding board and sand the orange peel texture of the Interprotect. It shouldn't take much sanding to get the orange peel texture down smooth and any over lap onto the old bottom paint will come off, leaving a very smooth and fair transition from repair area to old bottom paint.
Give a good once over with 80 grit on the whole keel, blow off the dust and wipe down with a tack cloth. Using a foam roller apply two coats to just the repair areas, a little overlap is ok. Not sure what paint you are using but most are touch dry within 30 minutes or less depending on temps/humidity. After the first two coats then put another two coats on the entire keel.
You should end up with a smooth repair where you won't see any seams at all.
