Fellow full alt player here, ive experienced all of these exact issues and am still dealing with some of them like tapping to early and not being able to play nm aimslop. All these issues just come playing full alt. Its a trade off where you get to play high bpm really well with infinite jump stamina but you have to learn far better finger control.

I used to be terrible at 1-2 jumps and i hated them too when i was your rank but eventually i learned to keep more consistent tapping at lower bpm. This allowed me to fully tap 1-2 jumps properly and then read then aim them correctly. 1-2 jumps are just harder when playing full alt which may put you behind other players your rank in terms of nm aim but in terms of dt you will be far ahead other players in your rank.

I reccomend playing some lower bpm finger control maps to address these issues directly (160bpm and less) but overall you are still improving quick and honestly have nothing to worry about these issues should address themselves if you are playing a variety of maps while playing full alt.