Help! I bit off more than I can chew! Body work

i used duplicolor automotive primer on the roof seam and already see rust coming thru paint. does the rust inhibitor sold in parts stores stop the rust? its just temp till i get the seam fixed. also my wife has now named it the RAT and hand painted a fat rat on the corner of my trunk?

I think my wife would have to moove out if shed try this with my duster or my roadrunner........!!!!???!!!! LOL......