M38A1 Troubleshooting - Starts/Idles Great, but won't rev up. Where to start?

I've had this M38A1 (1953) about a year and a half. New Fuel Pump and Carb rebuild when I first got it. It has run/started/idled perfect for a year and a half. Probably put 1000 miles on it. Only issue I've had in the year and a half was a clogged fuel filter that picked up some rust/trash from the tank (which I had drained when I first got it - had 12 year old gas in it). I replaced the filter probably 4-5 months ago, it fired right back up and has run perfectly since. I think there is some rust in the top of my tank, because the couple times i've filled it up completely I've noticed some rust particles in my fuel filter and that's the only time i've ever had any issues with it. And yes, I only use non ethanol gas and drive it maybe 100 miles a month so it's not sitting up.

I noticed it was acting a little funny this past weekend and thought maybe it had picked up some more trash. It was still idling/running good, but was a little tougher to start. I drove it about 10 miles, got out to help my kids put a boat in on a lake and left it idling for 10 min. When I got back in it would not go above idle without dying out. I started it probably 10x and it'll fire right up and idle perfectly, but as soon as you try to rev it up, it starts choking out. I put in a new fuel filter and after about a minute it fired back up and I was rolling down the road about 45 mph like nothing had ever happened. About 2 miles later, it let out about 6-7 of the biggest backfires i've ever heard and died. It'll startup instantly, idles good, but dies whenever you try to give it any gas.

Where would you start? Do you think it's a fuel issue or can an electrical issue come up out of nowhere like this while you are driving it? I pulled/cleaned the plugs - didn't see anything, was going to try and swap in a new fuel filter one more time, and the gas was getting pretty low and I started thinking there may be a pinhole in the pickup in my tank and the gas just got low enough to start sucking air in. I was going to add a gallon on gas to raise the level and rule that out. I also wondered if I could have gotten some trash in my car that was clogging the jet, but if it idles good I didn't know if that could be the case.