I would add some dye to the system, seeing that you have had it open, and other problems are possible.Makes finding small leaks much easier.
I have in the past charged a system with some nitrogen from a bottle,to check for any major leaks, but a slow leak may still take a few hours or days to expire the gas in the system.You can use shop air if that is what is available, just remember that shop air usually has moisture in it so a good long deep vacuum is a must after testing that way.
I have owned electronic leak detectors , like Tif, interdynamics and a few others.I have used a few yokogawa detectors and they are in my opinion hands down the best. Pricier than the others but way better.
Sounds like you found the main problem.The condenser gets hammered with debris and rocks from the road.Its no wonder it has a hole in it.
You can tie a piece of screen in front of it to help keep bugs out and ocks from damaging it. The plastic window screen is best, it doesnt rust , its easy to use and fit, and it is softer, giving a little padding to the condenser when a stone flys up to poke a hole.
Tooltopia has the yellow glasses kits for about 60 bucks. It come with dye for AC, engine, etc.good price.
Fact is stranger than Fiction