In first of 2 questions, i don’t know exactly how much keys, but in my advice for you, you can collect 10 up to 12 keys each normal waves is enough for you. You can also note that there are some enemies that never drop keys (Asteroids, Bomb, Egg Barriers,…). And any bosses that you can collect items from the chickens (not the boss), there are 10 firepowers and 15 gifts is maximum (not including the item that drop from the main boss)
All other questions:
1- The maximum dare points is 20,00pts. So idk, you can try it by yourself
2- No, it doesn’t. Beside, the spaceship’s hitbox isn’t involving to the collect-item hitbox of your spaceship
3- I guess so.
4- In my memory, the top-1 leaderboard of Space Race is under 5mins. I think you don’t have to care about this because the fastest time in Space Race is different between each mission (that’s because of what waves/bosses make the player fly longer or faster).
5- Yes. But it’s just in the theoretical calculation.
6- Bro, using IAMT or something else to mod 
try to ask someone else
7-
Well i guess it’s tier 50. (from the change in version 125)
8- Of course, because it’s a competitive mission, too.
9- Yes, it is
10- If i’m not wrong, there are 52 Keyrush missions in the current galaxy. (48 to 52, idk which number is exactly)