I read something interesting a while back by a marriage counselor. She said if you are thinking about getting married, think hard about your potential spouse. List the five things that bother you the most about that person. Then accept that you will never change those five things. If you can't accept that, don't get married. If you can't even think of five things, you don't know that person well enough yet, and should postpone marriage.
$7K is not a huge amount of debt. Depending on your combined income and ability to live within a budget, that could even be paid off within a couple of years. Lack of ambition is also not necessarily a big problem, especially if he is otherwise a good guy. It depends on you. Are you very materialistic, and need a certain higher level of quality of life to stay happy? Then maybe you would be better off with a guy who is more career-oriented, though there may be a trade-off in other aspects of life. I don't understand how the sex is still such a problem after you have talked about it. Was he really listening? Or just quickly getting defensive and shutting down the discussion?
The biggest potential problem might be your lack of experience with other guys. You might ruin an otherwise good marriage simply out of curiousity, eventually discovering that you were lucky to marry the right guy in the first place. It's too bad that you couldn't have met him later and had the chance to date around for a while first, because you would probably appreciate him more if you knew what other guys were like.
Good decisions come from experience. Experience comes from bad decisions.