I'd look at a walking belt and a bungee section to his lead. Whilst it might seem madness to have the dog fixed to you, having the lead clip to the waist means its much closer to your centre of gravity and you're not getting yanked in the shoulder, pulling you off balance.
The bungee section takes some of the sting out of a lunge too.
I was going to ask if you knew about ACE Freework which is almost what you've actually done there. Its a great thing for dogs, gives them something very simple, a series of easy 'wins', to keep brain ticking over but room for brain to processs in the background all the thing sthey're learning.
Chuck all the toys and puzzles you have down on the floor - grab some towels to hide treats under, crinkley plastic bag, something to step up/on, surfaces like an upturned box to put treats on.
Make sure there are free treats just for mooching around this big ole mess, he doesn't have to engage all the brain cells to find them.
Then sit on the perimeter and let him explore, if he comes and asks for help, then help but otherwise leave him to it.
There is more to it than that but you'd be better looking at some youtube vids or even better... get in touch with Tilley Farm and Sarah Fisher (she'd LOVE Pod... oh she really would!)...