I will be honest, I never photographer one. But from what I research, this is what you need. 

1. Long lens. Obviously the longer the better, because you can get closer. So with a good camera resolution, you can always do some cropping. 

2. Tripod. 

3. You have to use solar filters. From what I found out the main difference between ND and solar filter is strength. ND usually range from 1-10 stops, but for eclipse you will need, 13 or more stops for imaging and 16 or more stops for direct viewing. The big stopper you have mentioned is probably the one. Even so it is possible to photograph the sun with 11-stops filter, there are few things to remember. Don't look at the sun through the optical view finder. With 10 stops AND partial occlusion by the moon during an eclipse, it is possible to visually observe with a 10-stop filter, but the sun is still VERY bright. Use live view to frame and focus.

So you have to consider what eclipse have several phases and during the totality eclipse phase, all solar filters must be removed and it is safe to view the totally eclipsed sun directly with the naked eye. You can check how long it is going to be in your area here: https://www.space.com/33797-total-solar-eclipse-2017-guide.html It looking like it is around 2-3 minutes.

4. What comes to exposure, I found this guide: http://www.mreclipse.com/SEpho.....sure1w.GIF
This guide is just an estimate and I would recommend to bracket your exposure. You can test it under regular conditions, like you did. I think it will be very similar to other phases of eclipse, except totality phase
Also make sure you shoot RAW, so you have more flexibility with the image in post. 

I am looking forward to see your results and hear about your experience. 

Any advice for photographing the total eclipse that is coming on August 21st?  I took this shot of the sun using a big stopper and another 1 stop filter (so a total of 11 stops) but have no idea if this is too much, not enough, etc.

Thanks.