Made an account for my son, he shares my gamepass but can't cloud game..

Only the account that purchases the subscription can use cloud gaming.

I have Game Sharing with Xbox live gold, I share with my son in the next room, so he gets to play the games I own also, but he also able to download and play the games from Gamepass, but gamepass is not sharable like Gold is, I think ( as I am not 100%
sure ) that is shares with the system set to the Home Console. So in my experience yes you can download and play the Gamepass games as my Son does it with me.

I cant find an xbox companion app on my PC to sign out of do you mean the phone app? I cannot sign into the xbox with another account. It just keep automatically signing me into my account. I want to sign to xbox with my sons account so he can share my gamepass/games?

I am hoping you want to play the purchased game on both consoles. In that case, you don't have to buy the game again.

You can share your games, gold live and gamepass with your son. If you make your Xbox account as My home Xbox in your son's Xbox he will be able to play the games, gold live and gamepass you bought. And same way you can make your son's Xbox
account as home account in your Xbox console to get the games he bought. Your son can use his own account to play games but he may need to select your account just to start downloading the games you bought.

Note: You can only change your home Xbox up to five times in any one-year period.

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When you say can't share ultimate

Do you mean cloud ?

Or EA play or Ubisoft if so those are subscriber perks only

Meaning he can only access it

You can only access gamepass games and purchased games and play multiplayer on installed games that's it