You don't want to deal with future water damage. Remove your toilet and check to see if your flange repair is installed correct and level. Once this is done, replace your wax gasket and avoid caulking this seam until you are certain you have no more leakage. I've also heard many plumbers double up on the wax gaskets as a form of leak insurance, but will take time to settle and seal correctly.
If it is your intention of cutting the downstairs ceiling in order to repair the damage, you could place a few newspapers in the opening for a few days, and check it often for any signs of leakage before you patch and repaint it.
If you are uncertain if your flange is correctly installed or need a replacement flange, this is when I would call in a professional.