Mags are supposed to drop free. All my P mags and factory Colt GI mags drop free under spring tension from the followers on all my Colt 6933s, 6920s and my Larure OBR.
Sounds like your magwell isn't in spec.
You didn't have to accept the transfer if you weren't satisfied with the gun's condition. Most reputable online vendors will let the receiving FFL return the gun back to them if the buyer is not happy as long as the 4473 hasn't been completed. Once it's completed and transferred, it's your problem.
I've completely removed the locks from all my S&Ws that originally had them. It's easy peasy to remove. Plenty of online videos stepping you through the process.
I'd be passing too. I think the most I've spent per pound, even during the "shortage", was around $23. I'm buying my favorite powders online now for less than $20/lb.