"I cannot live without her!" should never be the true feeling. A great relationship should be between people who want to be together, not who feel like they "need" to be together. I've been in a relationship for over 4 years with the majority of it being long distance. There was no reason for us to be 'together' other than our desire to stay in a relationship and let our love for each other continue to grow. You say that you have issues to resolve that you feel are important to fix before getting more serious. What kind of issues are they? Financial? Conflicting future plans? Or are they problems with each other? My girlfriend and I have talked about getting married and we have agreed together that marriage is something that shouldn't happen between us for another 3 years or so because of our current circumstances. Perhaps the two of you need to look at your circumstances and see what it is that makes her want to tie the knot and you to be hesitant. If you care to elaborate on the issues between you to, maybe we can help more.
Avoiding co-dependence is probably healthy. The problems are probably located somewhere between career and future plans, problems in organising daily lives and related habits, causing a lot of irritation. More than I need feedback on my/our specific issues, I need to understand and learn how to ask the right questions myself to figure out what to do - thanks a lot for your help so far!