A few observations:
1. Your 70%+ fat intake is good. Most people try to limit fat intake and make this "low fat" and end up feeling exhausted.
2. You shouldn't try to work out in the first two weeks. You already have, so there's no damage done, but really, you're feeling tired because your liver hasn't learned to produce ketones fast enough yet. Give it time.
3. Carb up days? 48 hours? What? It's like a smoker having just one pack a week on Saturdays. Skip the cheat days and you'll feel much healthier. Trust me. The only people I've heard of doing this with a real reason for it are bodybuilders.
4. Your migraines are dehydration. Eat a pinch of salt with a tall glass of water, and you'll feel better in 15 minutes.
5. I don't know where you got the 50g max number. You eat enough to stay in ketosis, period. The only reason it starts at 20g is because practically everyone will go into ketosis at 20g. Then you work your way up, testing your tolerance with ketosticks.
1. Am I supposed to just eat clean carbs or can I still have ice cream????
You can make your own ice cream with splenda and cream. But the false sweetness will trigger cravings the next day.
Try refraining from sweet things for a month cold turkey, then allow yourself a cheat day... and you'll see how sugar really is an addiction.
It takes a LOT more willpower to have cheat days than not. Plain old low carb is a breeze. The food is awesome and there are no withdrawal cravings.
2. Should I go carb-less for 2 weeks or just 1?
I don't understand this question. I hope you're not going carbless at all. If you're asking about cheat days, I'd suggest every 4 weeks or none.
3. I keep reading that when on low carb diets constipation is a common occurrence. Is it?
Sometimes. Take magnesium (you are taking a multivitamin, aren't you?) and eat plenty of fat.
4. Is gas normal?... Because I have a lot of it!
I never had gas. It could be the fibrous vegetables, if you're not used to them. Especially gassy ones like cabbage.
Are you eating a lot of junk food with artificial sweeteners? They can really muck up your digestion. Note that any sort of processed thing on this diet (shakes, bars, cured deli meat, etc) is only low carb on the label. You might as well be eating Cheetos. Go for healthy whole foods like salads, steaks, veggies.
Overall it sounds like you know what you're doing, but I'm just going back over the basics in case there's something you missed. I wish you tons of luck!