Which change to make first?

[Splitlip]

The key to venting all the air from the bladder is trying to pull the dump valve over the top of the tank...not downward which although illogical as air rises, is often the most comfortable way to pull the butt dump, and what many people of do. Learn to pull the butt dump towards the sky, which is not a straight pull either.

good tip.
brings up the old discussion as to whether the dumps should on the divers side of the wing or not. (Remember DiveRite's debacle?)
My most used wing is a little 18 # donut with dump facing me. Using it as you described elevates the valve such that it functions perfectly. Until I thumb the dive I pretty much use the butt dump exclusively. And no water in the BC.
Granted I'm a www, but I have layered up to 5 mil for a 60 degree dive. (Yikes). Used my 30 # wing for that one! but the same results.

 

[Dirty-Dog]

Just curious, are you managing to do that with cold water (5-7mm) gloves on? I would thing that grabbing the line in that way might be somewhat difficult with gloves.

I don't dive cold water. I have, however, done it without difficulty while wearing 3mm gloves.
If you can't manage it, then tie a knot in the line close to that point. Or snip the line and tie on the big plastic cone from the end. Either would work, if the gloves have enough impact on your dexterity to be problematic.