I'm curious... since when is losing almost 10 pounds in 4 days not working? You cannot expect to lose weight everyday. After a dramatic initial loss, your body will probably need to recover before it drops some more for you. Don't worry about the scale. A loss of 1-2 pounds a week is the healthiest rate of loss.

Your mouth taste is most likely ketosis breath. Another sign it is in fact working. You can always use mouthwash. There are some brands of Splenda-sweetened mints as well, I'm not sure of the names.

I'm not sure about heartburn, though I think you'll find it diminishing with less carbs. My mom always suggests celery for upset insides. Something about the water and nutrients in it. I dunno.

Plenty of people don't give up coffee. If you don't notice it as a trigger, don't sweat it too much. Same with aspartame although that's a lot more likely to cause stalls and ignite cravings. There are some Splenda-sweetened sodas you can look for. I like Diet Rite myself.

Hope that helps. I bet you're doing well so far, so hang in there!