LME provides 35 gravity points per pound.
DME provides 46 gravity points per pound.
so, 7lbs of DME would provide 322 gravity points.
To get that 322 points from LME, you need: 322/35 = 9.2 lbs of LME
As for priming with DME... it's been a while since I did this, and I cannot remember that amount to use. I want to say 1.25 cups, but am not certain.
I've never used that yeast before.