Hi Trakkar,
I'm 70kg and 175 cm & have the SF 960 and 1100. Haven't used the 11800. The 1100 gets up and going a little earlier than the 960. I don't find there's a lot of difference between the 1100 and 960. Lots of overlap between them. Just my take on this, but if you go the 1100, I suspect you might want to unload the 960 and go 900 SF as there's more difference between them. Budget might not allow that?
My experience with my 7', 130L DW board and 4.5m Unit:
PnG 1010 gets going in 9-10 knots.
SF 1100 in 10-11 knots.
SF 960 in 11-12
SF 900 in 12.
As for wings, my biggest is a 4.5. I'm not sure how tall you are, but I think max wing size should be related to your height and not so much weight because if it's too wide in wingspan you'll touch the wingtips more often when trying to pump up on foil. I think you're right to ditch your big wing if it doesn't feel good. You'll find as you improve your wing pumping technique, you'll be happier with smaller wings. I wouldn't bother re-investing in a wing bigger than 5m, if youre up and going in 12 knots. Your technique will improve and lower that threshold.
DW boards definitely improve the light wind take off. So I would consider a bigger foil or a DW board if you want to get going in lighter winds as an option.
How much money do you want to spend and how much gear do you want?

Cheapest option? Unload the 7m and grit your teeth. I'd be inclined to do this first and see how progress goes for a few months. Given you're an intermediate, there's a chance you may get to a point where you want different gear to that which we are discussing now. Or you improve your technique to a point at which you're comfortable and no money needs to be spent.
If you're keen to do something now? Maybe 1100 or 1180 SF into the mix.
Or DW board?
Hope this helps.