Question: How many Xbox Game Pass Ultimate days would I get with this? (Saturday, May 14th,...

It depends. If you add that and then purchase Ultimate to convert it to Ultimate, you'll get 90 days plus the amount of Ultimate you add.

If you are adding it to an Ultimate subscription, you would get about 2 months of Ultimate.

That seems to be what is explained in the FAQ section of the game pass site. It states how many days you get of Game Pass Ultimate for engthl of subscription added.

There's a conversion rate when you swap from XBL Gold or Game Pass to Game Pass Ultimate, there used to be a limited time deal where it would convert it at a 1:1 ratio when Game Pass Ultimate first launched but I don't think that applies anymore. Before
you confirm the conversion to Game Pass Ultimate, it usually tells you how many months your current Xbox Live Gold subscription will convert to.

If you already have Game Pass Ultimate and want to use an Xbox Live Gold code then I think 1 month of Gold or Game Pass gives you 20 days of Game Pass Ultimate.

There's an FAQ at the following link, if you click on the question that says "After I join Xbox Game Pass Ultimate, can I still redeem Xbox Live Gold and Xbox Game Pass codes?" there will be a full conversion table: https://www.xbox.com/en-US/live/gold/upgrade

The early access only applies to the MP section.

Everyone will get to play the SP section feb 14th, but those with the online pass, also get access to the demo feb 14th, otherwise, they gotta wait three days[17th] to play the MP.

And I am not sure I'll play the SP demo, I'll wait til someone posts about it here and comments on how spoilerish it may be.

Hello welcome to the forums!

When sign up to Xbox Game Pass Ultimate you Xbox Live Gold membership and Xbox Game Pass membership convert to Xbox Game Pass Ultimate, actually the system clarify how many Months you will get for your active subscriptions. Then you can get back to the old
membership.

Regards!