Gosh I feel like I've tried everything.
Funny you mention dairysal No.5, my dad had great success with pure lanolin. Me, not so much.
I agree, coconut oil has helped me, and mine isn't so bad in the last few years since I moved to UV central in Central Australia. I can't help but get a huge dose every day and not I only notice it's really bad in winter when I'm less likely to have ventured outside.
I also notice that too much sugar sets me off so maybe a good look at his diet?
I try to have lots of omegas. I eat chia seeds/LSA every day, take linseed capsules and try to eat as much avo/good oil nuts and oily fish as I can.