Monetizing elsewhere is fine, but ideally it would be super great if you could give us about six months where it's just available in the fundraiser. That's just a request though.
About submitting, what a good question! Just the itch.io page is fine, as that's all I need for the bundle as well. Here's itch.io's official info on submitting into a bundle:
When the jam enters the submission period people who want to enter the jam can navigate to the jam's page to find a submit button. This brings up a game submission dialog where you can choose from games you've created on itch.io to submit. If you haven't uploaded your game yet you'll be guided through the process.
Because jam submissions are just itch.io games, you get all the features that itch.io provides. Your files and screenshots are hosted, and you can design a custom game page. A nice side effect of submitting to a jam onitch.io is that you automatically now have a nice page containing your game ready to be shared and distributed.
