1. It took me many tries to solve the command errors lol, but I think I managed to do this. Win7 setup was loaded and my wireless keyboard and mouse wasn't working (and I forgot to press shift+f10, sorry). I guess this is because of no usb3 drivers.
2. Then I tried to add usb3drivers (from Win7_USB3.0_Creator_v3) to the same boot.wim and it got bsod.
I have to catch a flight now, but I will be back to work on this in about 48 hours. The first thing I'll do is step 1 again properly.