Most vets suggest no surgery for LP unless there are obvious signs of discomfort. The ortho surgeon I use told me once that puppies need to have LP repaired to prevent problems with their legs not growing correctly. Mojo is probably past that point of worry, but I would still suggest a second opinion from a board certified surgeon.
So sad though that he is having such severe LP at such a young age.
Have you talked with his breeder about this?