It is correct to put numnah on first, then saddle - I am lazy, have a simple high wither numnah which I attach to saddle, and then put the whole lot on together - tsk, tsk!!
Cross tying, not for me, I would if I had no other option, but not on a daily basis - I think better to get them used to whatever it is, rather than tie them down.
Pig oil against mud fever - but am guessing if you having an issue with the Keratex powder, the pig oil won't make the standing still to have it applied issue any better.