Red dot placement

I know lots of questions. Sorry...

Is placement of red dot better over grip hand or towards the end of the barrel?

Unfortunately, all of the above.
It’s trial and error and what works for you.
Looking down the line, there all over the place.

Try it in different positions. Don't over-think it.

Welcome new shooter. In my opinion, worth all of price paid, a scope way out on the end of a barrel will magnify rotation movement from the wrist. Basic mechanics and physics. To a highly skilled marksman it's less of an issue but detrimental to most others.

Ideally, you would want it at the center of rotation which is the wrist but that's not possible so most locate above the magazine taking note of breach gas and shell ejection issues. Good luck. But like others said,  A lot of this sport is thinking on your own and trying things out

Depends on the dot and the gun combination. Larger tube style dots typically have fewer placement options (eg center of 1911 slide), micro style dots have a bit more placement flexibility but at the cost of a smaller viewing area. Realistically it depends where you want the weight on the gun.

I like them as far back as I can get them. Without getting in the way of the hammer.

I like them towards the rear.