Glad things are improving. Be consistent with maintaining high cl levels while the water is cloudy. Are you testing your pH while the chlorine is high? That will give false high pH. With the Taylor K-2006, you can test pH if the chlorine is lower than 15 which is higher than most kits will allow. I wouldn't worry about raising alk any right now.

You can try a little trick that some of us use to help our sand filters filter a little more efficiently. Adding a little DE will help you filter out smaller particles than your sand can get by itself. Read more about it here:

http://www.poolforum.com/pf2/showthread.php?t=3742

I can't help with the heater issue. Somebody else will hopefully chime in about that.

Hope this helps.