Well, I wish you the best of luck. I knew DS was bright before VT, but I had no idea he was PG. Gee, I couldn't believe the speed of those developments once the VT kicked in. You might be amazed. You just don't know how much the vision is bothering him until you start getting into the VT more; my guess is that he's probably compensating in some capacity right now. The really good news is that you're getting it sorted now rather than later.
DS had visual spatial deficits, not converge issues as far as I'm aware. He was born with torticollis (head tilting and neck muscle) so it was somewhat like a stroke with the left side of his body and the neck muscle. He had very poor eye-hand coordination (perceptual particularly) and fine motor skills; both the eye-hand coordination and fine motor skills have improved but they're probably what not what they should be. DS still has some body-space issues; that's a lot due to the torticollis. He's still a bit hypotonic and lacks the stamina too. Yep, I know how that can be annoying and frustrating some days.
Since DS did VT, he's been in neurofeedback and between the two it's made a huge difference. It's not a magic bullet and not an overnight solution. Yet I swear by VT and NFT. They're both really amazing therapies.