For your number 1 and 3, spears should do the same damage if mounted or on foot, it's speed that should be the addtional factor.
for 3, i agree that ta couched lance shouldn't move to much, but it should still go from left to right. but it's zone of attack should be very frontal. i've seen some lances be couched and go way off the sides. thats not right
for 4, i agree that a player should be able to protect themselves while getting up. it's realistic, your first instinct would be, shields up.
for 5, this kind of goes with 4, but no a player should just drop right where his horse dies especially if there was momentum. The rider should get flung off. but i think the rider should take much more damage. people die all the time from getting flung off horses.
from 6, this is the one i completely agree and support. i've used the tactic alot as a MP horseman. Riding in and saving allies. it's super cheese i know, as it should knock over everyone equally. Horsemen should have to be extra caution in not ramming in to allies instead or pretty much disruption a whole allied infantry charge.
For your point #1, IDK if you're disagreeing with me or if you're doing a change suggestion, but just to be clear, atm horses are so tanky that running head in at full speed into a spear stab barely dents the horse's hp. Yes the rider takes more damage but most of the time, it's the horse's hitbox that catches the stab and not the rider.
For your point #2, indeed, I saw some couched lances initiated totally on the right and I got couched by their lance being suddenly completely on the left. They can turn it too fast.
For your point #3, I disagree. For realism's sake, if you fall from your horse while it's galloping, it will most definitly take you more than 1-2 sec to get back up because you'll be extremely hurt (hell some ppl outright die from falling off of a horse) and you'll be dizzy/stunned from your fall. For balance's sake, currently when you are bumped by an enemy horse you stay on the ground much longer than when the rider get's unhorsed.
For your point #4, if they get damage proportionnal to how fast they were going when their horse died, to a point where it could be lethal unless they are full hp, I'd agree with this change. I just want unhorsed riders to be "punished" for balance reason the same way an archer is "punished" if he is by himself and is flanked/ganked by an infantry.
For your point #5, indeed, it's really cancer.