We all get days like that Alex, in my paddleduck build, in total I ended up making 4 spool valves (2 had far too much leakage in the bore of the valve)
I too had problems getting it to turn over smoothly, the best advice I can give you is to just take your time and work methodically through where it is sticking. On mine it was only slightly binding up, but it was binding up in quite a few places and so all that "slight binding up" added up

I ended up slimming the con-rods down using a bit of emery held on my surface plate, that along with fiddling with the crosshead bars after enlarging their mounting holes in the top plate, got me to the point where there was much less resistance. Then I left the fiddling until I had it ready to run on air and did any last fine-tuning while running it in.
Stick at it, it's coming together nicely. We're starting to see an engine appear

Tim