Hi, I think you are worried to a good start but I suggest you change the following.
1- don’t use kk2.1, rather go for an apm2.8 if you want something cheap, reason is APM gives you alot more functionality such as GPS return to home and auto hover.
2- I suggest you use a bigger battery if you can, maybe a 3000mAh with a lower C rating of about 15 to keep it light.
As for your questions I suggest you read this guide How to choose the right motor for your multicopter drone as it answers your questions about motors… but I think you are on the right track 