Egar, something I've found about starter fluid...it can be real tricky getting it into the engine with the stock airbox. You might try it without the air box or at least without the filter inside. If your timing is off, any slight back fire could burn up your filter element. Also to get the starter fluid into the engine, turn the choke wide open, spray, kick it once with the ignition off to suck charge into cylinder, close the choke, turn on ignition and kick. If your sure the starter fluid made it into the cylinder and it doesn't at least fire, sputter, or pop...you got no spark. It's a juggling act to do a proper spark check with no starter motor, by yourself.
On the petcock thing, I have had the same problem with freshly rebuilt and installed ones. Try redoing it and lube all o-rings and gaskets with wd40 or even a light grease. I've found this can really help the o-rings seal up tight without galling or twisting.