Well, it was bound to happen.
I had some successful trades in the past but being a more-or-less Bisq noob I have finally stumbled onto the issue of someone attempting to scam me.
So, here’s how it goes: I was already about to trade some BTC on Zelle for slightly lower than the current BTC market value at the time. The buyer left me hanging all overnight and then in the morning sent only a PARTIAL payment (only $300, not the promised $370). They messaged me first thing in the morning and said, “Sorry, it’s going to have to be a few days because of Zelle’s transaction limits for new users.” I was politely like, “Uuuhh, well you should’ve only listed what you were able to pay in the first place.” At first I asked for him to take back the $300. Then I saw the payment was still processing and my BTC wasn’t released to him and I was like, “Okay, nevermind that. Just next time only offer what you can afford at the time.” So this douche has STILL locked up my transaction and in effect they’re going to be able to get my BTC for way under the market value if the wait’s long enough. (Of course they should have $70. It’s not like they’re 12 or like they don’t have a low enough income where they can’t afford soap or pants.)
Fortunately I have not done anything with their $300 deposited in my bank account. Of course I’m not going to just make off with it and ask him to refund my BTC. That would be pretty sleazy.
My main question is how would I mitigate instances like this happening in the future? It looked like they signed enough previous transactions when I clicked on their offer. Anyway, that dude’s a douche. (Fortunately, the platform rocks and I’m not placing the blame of one douchie douche’s actions on the entire platform. I was just waiting for this sort of thing to happen one day, since it happens at least once a lot of times to even a lot of savvy users.)
Another thing. I don’t know if this is worth mentioning but can a person really pick a cheesier handle to put on their bank account or gift card than “John Carpenter”?? Yes, I have not lived in a cave- and I’ve seen “Halloween” and “The Thing”!
Anyway, thanks in advance for all your help! 
Peace!