How much do morning stars weigh?

Probably not more than three pounds. That's more than enough weight. Also, there is no standard size. If the one you have is too heavy, just practice with it.

average weight for a 14 year old should be around 8-10 stone ( not sure what that is in pounds) although as long as u eat healthy and are reasonably active it doesnt really matter, some people are just naturally heavy, or large, or indeed skinny. like me, im 22 and 6ft 2" and weight 11 stone

Seeing that many maces were used in combat, it seems that fighters in olden times were a strong old bunch!

Indeed all weapons, maces, swords, spear points, arrow tips, etc, were made in forges.

They weren't heavier than a sword. Don't take video game depictions too seriously.

This might be of interest to you:

https://www.youtube.com/watch?v=O-y6oirEsZA

Venus' mass is 4.8675×1024 kg.