The plug you are using is fine. The ES vs EG is just the stye electrode. They both are the same heat range. I use the ES all the time.
Your plug fouling is a jetting issue and I chased for a long time on my bike until I fainally bought a JD Jetting kit. It was well worth the money. It comes with a unique tapered needle that realy cleans up the carburation.
If your cap is melting you may need a new one. If the clip (that attaches to the plug) is loose it can get hot. That could be causing your plug fouling too but I'd still get the jetting kit.
BTW, have you every heard of a period? ;)