Ever try reverse overhand grip EZ bar curls, even with a regular BB? Can do either with a thumbles (false grip) or usually thumb under the bar/EZ bar overhand grip. Might also suggest switching to only hammer DB curls for a change. Reverse curls and hammer style curls are very much overlooked biceps builders.
Wonder if you have a calcium deposit in your wrist, to make that cracking and popping noise. Does any of your wrist problems happen with pulling movements only, and not pushing/pressing movements? Even advancing arthritis could be a problem...hopefully not.
May also have nerve displacements in the wrist than could cause undo pain. Wrist and forearm massage could help, even with a calcium deposit problem. Lot of wrist problems have their start in the forearms and even the elbows, as the nerve paths travel down into the finger tips and blockage could occur. Not that uncommon.
Good Luck..
Good Luck..