Question about a old mad bypass repair

The fuse blowing is probably directly related to your alternator output. After the battery runs down following a start or a long crank, the alternator goes full field for a little bit trying to get the battery back up. (This is why alternator belts squeal when people fire up a car with a low battery) and can easily supply more than 40 amps. Usually around the alternator rating and sometimes more. @67Dart273 is right on again. You need a bigger fuse.