I don't think bearing pre-load is going to be a factor in keeping the bearing from spinning on the spindle. If a bearing is too loose on one side (the top) it is way too tight on the other side (the bottom)! A loose bearing can burn up just as fast as an overtightened bearing.
The bearing got hot due to low lube, or way way wrong pre-load, then briefly seized and caused the bearing to spin on the spindle. Simple fact is that the spindle is now too small for the bearing.
There is one shot at holding that loose bearing on the worn spindle. Locktite #601 or #603. After that, time for new spindles/bearings.