You could have flipped the M/C seals when pushing the pistons in the calipers back, in any case I defo would suspect the M/C!

Has it got any better after driving?

Really you should replace the rear shoes, it seems almost silly not to for what they cost, as you have serviced the rest of the braking system!

Handbrake should be self adjusting, although there should be an adjuster on the cable, but this never needs touching unless a new cable has been fitted etc, this works ok as it's seperate from the hydraulic system!

Martin