My favorite beer is an AG version of what you are proposing.
I use 8# Maris Otter instead of the extract, and crystal (49-64L) and cara amber (0.5# each) or 1# crystal if I don't have the cara amber. (I think yours may come out a bit pale for a bitter, but that may be what you want.)
If you are using LME, your OG will be less than mine. If you are using DME, it should fairly close to mine (about 1.056). I think these are a bit high for an ordinary bitter, but certainly not excessive. Just call it special or extra special bitter. They are also session beers.
I've used 1275 and 1068, and definitely prefer the 1275. I've not used the 1968 yet, so I can't comment on it.
As for the hops, I use 2 oz NB (60 min) 1 oz Fuggles (30 min) and 1 oz EKG (5 min) and it tastes just right to me but I like my beers to be slightly on the hoppy side. You obviously have impeccable taste in hops.

There are plenty of bitters that are more highly hopped than that, but to be fair, there are plenty of bitters that are less hoppy.
I sometimes add 0.5 - 1# flaked barley (but it does need mashing). It gives a nice grainy taste, and helps head retention. I only ever do this if it is going to be bottled.
Hope this helps,
-a.