It is indeed a hard decision to make. I am assuming you are very much in love and feel he is a worthwhile guy except for his debt status.
When I was a single girl, I was very rational. This kind of scenario only holds one answer for me - don't be crazy, leave the guy. Only when I fell in love, then I realised love is indeed irrational. Life would be a lot simpler if we operate on rational mode but the true fact of life is that we do not. Especially not when in love.
So, no one here can tell you what's right or wrong. You'd have to decide for yourself and think through all angles. Blame no one else whatever the outcome which could be many:
1) He's worth your time, stay by him as he is repenting each day and is a totally changed man. He is very caring towards you and there's no reasons to doubt his love except for his debt status. Solve problems together.
2) He's worth your time now. But he will change and go back to his old ways a few years later. He will ask you for money to help settle his debts. He's sometimes not that into you. Other times, he's caring to the max.
3) He's not so worth your time. Besides this debt, there are other irritating habits you cannot stand. You aren't sure. Live is always filled with uncertainty and petty quarrels.
4) He's not at all worth your time. You thought he changed but he never did. It was just a wishful thought and he's more in debt than he can ever be.
The above are just but some possible scenarios. But whatever it turns out to be, it is important that you go on to whatever decision with the fullest knowledge of the possibilities.
For myself, I thought I found a totally stable, honest, reliable man. He looks and acts totally trustworthy. Only after we started dating, then he got himself into debts through stocks and shares trading. I was devastated not because of the debts, but the fact that he lied. Not just once or twice. He lied about happenings whenever I suspected something was wrong. In a relationship, I thought honesty held the highest priority for me.
I was totally devastated and did not know what to do. We were already planning our marriage. I considered all the possibilities and reminded myself that this will forever be a black mark in our lives. I told myself I still had a choice then. A choice to walk away.
But my choice? I chose to marry him. We have been married for three years now. He's very frugal (he was a frugal person from the beginning) but never stingy towards me. It was and is still a huge gamble for me to marry someone heavily in debt and with whom I'd not have a financially stable life with. But whatever it is, we have had this three years and still counting. If I had given up, I would not only not have this three years but also not the chance to experience having a good husband which he has been to me.
But this is just my personal sharing. There isn't a right or wrong to me to date. Life is still long for us with so many years ahead to face. If things were to go wrong one day, I can only pray that I will not hate and become bitter. But at the very least, I am very sure I cannot claim to have been ignorant. I walked into this relationship with my eyes wide open.