If you're business is investing in stocks, there would be no need for that activity to be in an "S Corporation."
As far as using the business credit card, for personal use or personal business use (not related to the S Corp), it happens sometimes. You just have to make sure you don't continue doing that. Those purchases you did make would be considered shareholder distribution on the S Corporation tax return. It is not an expense to the business. If these are expenses related to your personal investment account, you would still be able to record them on your personal tax return.
You will have to pay down the debt with either business income or personal income. It doesn't make a difference which.
Not sure if you were considering this (when you said you want to start all over), closing this "S Corporation" and opening a new one will not do anything about the debt. Plus you wont be able to dissolve a business with open debt anyways.
In a summary, ff the problem was that you didn't open a business account but used the business credit card to pay for expenses on personal account, which are business related, you will be able to write them off on the personal return (as long as they are business expenses).
