Fluid maintenance and fixing any issues as soon as they arise are the key to longevity from any vehicle.
Trans fluid, p/s fluid, oil and coolant can not be serviced too frequently, most manufacturers “recommended” service interval is way too infrequent imo.
No vehicle has ever died because it was maintained too well.
Sounds like 2 separate (but maybe related) issues. First is a parasitic draw that’s killing your battery, second is the crank no start.
The first step is always scanning for codes (if the battery is dead, connect jump pack or cables and try to start the with jump pack or cables still connected check for codes… You’re looking to see if something like a cam or crank sensor code pops up. If the battery dies the codes erase.
If the code scan doesn’t give any clues the you are going to need to verify that you have spark. Several ways to do that, just check out a YouTube vid or 2 if you need a walkthrough.
If your plugs were wet and smelled like gas I’m assuming you’ve got no spark. If that’s the case determining why, will take a bit more diagnosing.
Not much you can do, you’re going to need to verify the ECM has the ability to open and close the purge valve. You can manually apply power and ground to the purge valve to verify if it has the ability to open and close but without a bidirectional scan tool that about all you can do.
One caveat is you could technically watch scan data and wait till the ECM to command the purge open on its on to check for power and ground at the purge. You’d need your test setup in place and just run the truck watching for the purge to be commanded open on scan data.
I’m assuming you’ve already replaced the purge valve and the code came back… If so make sure you didn’t just get a bad new purge valve, they like to be DOA straight from the box in my experience.
What you killed depends on what wired shorted and where they’re wired into. There’s literally no telling with aftermarket wiring jobs. Hopefully it’s just a smoked fuse but without having any real useful info who knows.
The timing marks on the cams 100% will have to match their corresponding side you can’t time the right bank with the “L” and vise versa.
There’s always a chance of aftermarket parts being bad straight from the box, in this instance however that’s probably not the case.
The fact that the ECM set a p0420 means the O2 is functioning, in all likelihood the cat was bad already the ECM just didn’t know it due to the O2 sensor failure.