Honestly , have no clue oxymetholone has a melting point of about 360°f . Ideally, you wouldn't have to heat it to its melting point , but I always dissolve my raws in solvent first so I dont have to use as much heat.
You dont really have the best set up either , you should never use a water bath to heat your brew . There's so much that can go wrong with that . You should atleast have a hotplate , preferably with a magnetic stir bar and at least a cheap laser thermometer (for future reference).
Aside from that yeah crank the heat up on it slowly and see if your can just force it into solution . Just keep in mind guaiacol evaporates pretty quickly so if you leave it on open heat to long its not gonna make your problem any easier.