KHB......... is the caramalt 50ebc JW caramalt.
If it is, put it away and use 145ebc crystal!
The caramalt is used to build the malt profile in pale lagers...... not dark proters.
I used it for dark beer duty when i started out mashing because all the writeups on porters, bitters ect said the malt should take on a caramel quality. The caramlt wont do this........... it will give you a honey like sweetness that cant compare to the caramel qualities of 145 ebc crystal malt.
mash temp sounds right, i would check your thermomiter as well. Those figures look more like a 64 deg mash, ecpecially with all those specialty grains in there.
Also........ high carbonation can give the impression of lower body.......
Other than that use 5% flaked barley in the recipe.... they are great for body in a dark beer!
cheers