you say your "pointer is off by about 15" degrees.....are you saying that the timing tab is not positioned properly or that your timing is out of whack?

In my unqualified opinion, it sounds like your timing is way out of whack in conjunction with other problems. Whatever existed before was exacerbated by the installation of the carb. Not necessarily by the carb itself, but through the installation process.

You'll need to get some firm baselines and provide more info. What are the specs on your aftermarket cam?