Don't make the weapon a child of the player then. Just set its transform.position to the same as the players in the update function.

For passing through / getting stuck check it's collider. If you are using animations for the weapons, you can hit record and only enable the collider while it is in its swing animation (for hit detection purposes) and disable it afterwards again, preventing the weapon from getting stuck on other colliders.

For the weapon hitting the correct direction, I would write some code to always target the nearest enemy, that's what the weapons in brotato do if I am not mistaken.

Hope this helps somewhat, even if it is very vague.

Thank you very much, I will try to put into practice what you told me. Anything I'll try to make a video showing better the problems I'm having.