Upvote:2
First of all, your visa is not valid anymore, if you have exceeded the allowed period of stay (15 days).
Even if different member states operate with different details in the implementation of the rules, extending your Schengen visa due to urgent medical issues (incapability of travel) should have been easily done, both for your wife and for you as a close relative. Your problem now is however, that an application for extension must be made before the visa expires or before you reach the allowed period of stay.
Your best bet is probably to contact the Spanish immigration authorities before going to the airport and try to solve the issue.