Solved - rear brake relay defective
After going over every electrical component and connector that I thought I could have damaged when I replaced the fuel pump, plus going through all the fuses, and relays, the last and final check I did was to completely replace the brake relay in the left rear compartment and PROBELM SOLVED!!!
What's really strange is that's where I actually started to look for the problem. I switched another relay (exactly the same) from my fog lights, and tried it in the brake relay location and switched the brake relay over to the fog lights. The fog lights worked but the rear brakes still wouldn't function. So I switched everything back.
Why replacing the brake relay with a completely new one did the trick is another mystery.
But, the long story is, the fuel pump replacement had nothing to do with the brake lights going out as I suspected. How the lights went out coincidently at the same time as the completion of the work on the fuel pump is why I chalk it up to "its a Volvo, what do you expect".
Thanks for sticking with me on this one.