Yeah, it looks like you're about 15dB down at 38Hz. If you have a proper WAF battleplan, I would try 2 or 3 different room positions with measurements after each. You're battling the room's black hole it appears.

You might want to try messing with phase to see if you can better integrate the sub with your mains seeing that 75Hz kerplunker. It looks like you have another one at 90Hz too (which I have too). Does the VTF3 have a 0/180 toggle or infinitely variable dial?

Show us a graph out to 120Hz if you can. That will show how smooth the sub blends with your mains, very important for smooth transitions.

Working around that 15dB canyon at 38Hz is gonna be tough though.