When you say , "If I can stand it" that suggests to me that maybe you should just forget about ATG for the moment Tubby. No passes should be a test of endurance, I don't think. If it's as sore as that then I greatly doubt that the upper dermal layers are having a chance to recover before the next onslaught. Maybe try just the one, light pass with the grain. If you're still a bit stubbly rinse your face with lukewarm water, lather up again and lightly go over the bits needing touched up (Hush PigCat you wee rascal !) across the grain, or, if need be with the grain again. The Merkur is a gr8 brand & Feathers are sharp enough that with that combination you shouldn't need to apply any pressure at all, the weight of the razor will do the work for you.
Keep the Faith Bro.
JohnnyO. :shave