David
Sorry the New Year hasn't exactly got off to a great start for you. Never the less , Happy New Year anyway.
Dryad's suggestion is good. The usual advice is a really good clean up , drain hole clear , no rough nicks / burrs ( dress /rub down as
necessary ). Clean hands when re assembling and a dab of clean oil on the new seal when you insert it.
The rear axle brake drums will need a good clean up. New brake shoes on the rear , if they've become contaminated. File a small chamfer
on the leading edges , to stop brake judder.
Item Failure sheet 4 leak nearside rear braking .. did the tester show you which union was the culprit ? Don't overlook the fact that it might be " diff oil " rather than brake fluid , if the seal let go and oil has been thrown around. If it wasn't crystal clear , a clean up of the rear brake lines , followed by holding down the brake pedal hard for a minute or so , should produce the evidence of a leak.
I always put a brake pipe sealant on when putting on new pipes / joints ( a belt and braces man as you know ). e.g.
http://www.frost.co.uk/brake-and-pipe-seal-75ml.html there are other suppliers of course.
The imbalance of rear braking will have been affected by seal leak and brake leak ( ? ) and this , in turn , will have impacted on the handbrake /parking brake efficiency.
I'd tackle it by cleaning up , new parts fitted , leak eliminated ,copper ease applied , brake fluid topped up initially.
Slacken the handbrake cable right off and adjust the rear brake shoes. Once you're happy tighten up the handbrake cables.....individually
...... noting with the first one how much thread is exposed , properly adjusted to the relevant number of ratchet clicks. Then slacken number one cable off and adjust the other. Then reconnect the second ( to the previously measured place, so both cables operate together. Both rear wheels should now lock solid when the handbrake is applied.
Front brakes.... check visually , with the brake drums off , that nothing is amiss. You can always get your son to operate the
brakes gently
for you ,working on one side at a time ( i.e leave the other side drum still fitted or the wheel cylinder will pop out !!
Have two large screwdrivers / tyre levers , whatever and brace them against the brake shoes, using the lip on the brake back plate to keep the free ends steady. That way you can see if the wheel cylinders operate as they should. Replace the drum and move to the other front wheel to check that. Hopefully it will be a simple adjustment / brake bleed to get rid of any air.
Scream , if you need a steer on anything else on the list. Keep plugging away.
Bob