I also have a glass-top stove at home. So far, I really like it: the heat is very even and there is good heat transfer, provided the pan makes good contact with the surface (one skillet I have has a bit of a lip, which makes it heat more slowly).
I've slapped skillets and pots full of water around on mine, and have yet to break it. I'm probably more careful than I would be on a metal range, but it seems sturdy.
But to your points:
1) There is no way cast iron could melt the glass. Iron melts lower than does glass (1200*C vs. 1500*C), so before you manage to melt your stove, your pan will be a puddle. It may, however, be possible to deform the stove top if you let an empty pan heat for some time. I don't see why this would be more of an issue with cast iron than with any other piece of cookware.
2) A heat defuser will work fine. Don't get the kind that is designed for use with gas, but anything else should work fine.
3) The burners on my stove are smaller than my skillet, so I find I need to move the skillet around to heat the edges. Also, flat-bottomed pans and pots seem to be much more effective on the flat glass top, as conduction seems more effective than radiation here. I polish the bottoms of my pots to get better heat transfer, although this is just me being anal.
Also: cast iron can't scratch glass. Glass is much harder than iron (see this wikipedia article), glass having a 6-7 on the Mohs scale, iron having a 4.
If you are having trouble with honey-wheat bread sticking in your cast iron pan, there are several things worth trying:
Make sure the pan is well seasoned. There should be a smooth, continuously black surface over the entire food contact area of the pan.
Spray the pan with oil before adding the bread. This may or may not work but is probably worth a try.
Do not add the loaf directly to the cast iron pan. Put it in on a parchment sheet, so that it is not in direct contact with the oven. You will have to peel off the parchment afterwards, but it should reduce sticking.
In fact, in some versions of no-knead bread, this is the recommended method until the loaf is well set, then you remove the parchment for the latter part of the baking to facilitate bottom crust development.
Honey-wheat breads are going to be inherently more sticky than a pure white bread, especially because of the sugar, and because the whole wheat bran in the loaf tends to cut the gluten strands, making it hard to get a tightly stretched gluten network on the outside of your loaf, which is one of the things that makes it less likely to stick.
Best Answer
I encountered this problem making Bulgogi. I found that the surface should be well oiled/greased, and as much marinade drained from the meat as is possible. Baking soda and vinegar did a bangup job cleaning off the residue - my griddle was fine, but you may need to re-season.