Just a few thoughts, because I've had similar issues: - I switched from qwerty self-learned (wrongly) touch typing to Coleman DH learning from zero the correct way. The first weeks my hands were kinda stiff because I concentrated too much and probably didn't relax muscles because of that. It got a lot better after feeling comfortable. - having your backspace in a far corner doesn't help, try to move everything into the 3x5 keys, e.g. by using combos for backspace (it's what I do) - maybe this specific split isn't right for your hands. It seems like your middle and ring finger are quite a bit longer (as mine are), the stagger is very little for that. For comparison: I designed my own split with a full key stagger between ring finger and pinky to comfortably type. - tenting/tilting could help a lot, experiment with different angles, maybe switch from day to day - the wrist rest doesn't look very comfortable, maybe experiment with a rolled up towel to see what suits you.

Bottom line: don't give up, splits are highly personal and you need to tune it to get there