How do I get the game pass on my PC when I already have it on the actual xbox console?

If you only have standard Game Pass for console then you'd either need to buy the game for PC as well or buy Game Pass Ultimate (to have both console Game Pass and PC Game Pass for free). Not all games can be played on both console and PC even if the game is available on both.

I have ultimate on the console

I am trying to download MW5 Mercs, the app is trying to charge me for it.

Now I'm not sure if this matters, but even though I am logged in on the same account to play games, the store has me logged in as a different account. Could this be affecting the Game Pass?

Then as long as you're signed into the same account you should have it. What game are you trying to download? Have you been trying to install it from the Xbox app?

So this is where I am running into other issues now.

I joined xbox live a long time ago, like back when the 360 was fairly new through this Xbox Live Family system. My account was then given it's own "email." However, when I try to use this email to switch it as my store account it does not recognize the email and says it does not exist. Yet I am signed into Microsoft website itself with this same email.

Is there anything I can do to resolved this issue?

Is there a way to make it so my xbox account is connected to the email I actually use instead of this xbox live family one?