Mathematically, it is technically possible to just hit 75% efficiency on a 1.090 beer with a single sparge and 15% boil-off, but you need to hit 100% conversion. Homebrew shop-crushed grain can make that conversion rate difficult, since it is typically under-crushed, in my experience. If you don't have the luxury of your own crusher, a step mash to a higher temperature alpha rest, a longer mash and even a brief decoction can help you get closer. In addition, on such a big beer, you should get another 4-5% with a second batch sparge, with no real risk of oversparging, even without collecting extra volume and a longer boil-off. Collecting extra sparge volume and boiling longer would also help.