I have no problem boiling 4 oz sugar in 8 oz water. You'not making simple syrup. And unless you burned the pot, the burnt taste didn't come from the priming solution.
I've used corn sugar, DME, and table sugar and really haven't noticed any difference at all. I used table sugar most recently in a milk stout because I realized at bottling time that I was out of both corn sugar and DME. It turned out just fine, and carbed up just fine in a couple of weeks. Table sugar is he cheapest, so...