They can get your name, address, amount bought, and wallet you sent it to if you buy with something like cashapp or paypal. If you do cash in the mail, they could only get the wallet address you sent the money to, and how much your account bought, but not necessarily who you are or where you from as long as you connect through Tor or a good VPN with javascript disabled.
And yes, the feds can force them to hand over any and all information about your account that they have in their posession.
And yes, the feds can force them to hand over any and all information about your account that they have in their posession.
localmonero.co has an ⚠️onion address⚠️, in case you didn't know.