Looking at your other threads, I see Theo is 11 months old. What you described sounds very dangerous.
1.) Was he walking nicely on leash until recently? The 11-12 month range is often one of those teenage phases where they test you.
2.) How much exercise does Theo get outside of leashed walks? Are you exercising Theo before you go on your walk? It sounds crazy, but for Kimber's first 2 years, I had to take her on a pretty strenuous off-leash hike before we got on the leash; she just had too much pent up energy. If you can do a quick but good paced game of fetch or something else to take the edge off Theo's energy, you may see some improvement.
3.) What kind of collar are you using? Different labs respond best to different collars, so there's a bit of trial and error. If you decide to try a prong collar, I suggest doing some research to make sure you are using it properly. (there's no judgment; until her spinal injury, the *only* way I had control over Kimber was with the prong collar. I had our obedience trainer help me size it and spend some one-on-one time teaching me how to use it.)
Meanwhile, I would do a lot of leash practice in the yard and in parks, and try to walk him in less populated areas until things calm down.