You haven't mentioned boom height. Raising the boom adds "lift". That's why you see a lot of foilers with booms shoulder to nose high. Sam Ross in his foiling tutorial videos puts them pretty high if you want to see an idea of what it looks like.
On getting on the foil, bear away on a reach to broad reach. Pumping helps a lot. So does hopping the board if you are in both straps to pop the board clear of the water. Do a search here if you can as there've been good threads with lots of videos on how to do it. The key is getting clear of the water and technique definitely helps. Once you are clear then the foil can work it's magic. Don't do like a lot of people starting out - try to force it high. That takes energy and why you may have gotten out of the water a couple of times and then flopped back down like a fish. You just have to be clear and can even skip a couple of times as you gather speed.
Make sure you are looking at the horizon and not the nose of the board. That reduces porpoising a lot. Also, the more consistently you can keep pressure on the harness, that'll reduce variations caused by wind pressure changes. A lot of people reduce their harness line length to maintain an even pressure. It's not uncommon to start out with your harness lines too far forward. Make sure they are balanced. Having too much back hand pressure pushes the back foot which causes you to go up every gust and back down every lull.
Your back leg burning is one of the signs something is amiss so good that you mentioned it. Most of us like having a fair to a lot of pressure under the front foot which is very different at first from regular windsurf where you can lean back and out and let it motor on. We're more over and on top of the board until we begin to accelerate. The faster you go, the more front foot/harness pressure you'll want to have available.
The Foilglides are good sails. You should be between 1-2 m less than you'd normally sail with just a bit of experience. The really skilled foilers, if they are hitting their jibes, can get by with less because they are touching down rarely. You are likely having to get powered up every time you come down hard or transition with a tack or jibe. But, that'll be you some day.