It seems like alot of it could be proper exercise, APBT need lots in general. He needs more than just a walk. He needs a work out. If you have a treadmill, you can make him use it for a half hour or so at a walk or a trot to help take off some of the edge, or if you have a fenced in back yard play with him alot before you take him out. Oh and in some places, using treadmills is illegal (apparently you're training them for pit fighting if you run them on a treadmill, so either do it discreetly if it is illegal, or find another way!!)
If you opt for a halti, or a no pulling harness, get a double clip, or a short handle leash or anything like that, and attach both the harness/halti and the collar to the leash incase one of them breaks, you've still got a back up. Make sure he's got tags on and even better is to be microchipped aswell.
Such a pretty dog might get stolen if he is seen wandering loose!!
Try getting a dog pack that fits him properly, fill it with sand in waterbottles, anything that will make a basic half hour walk a complete work out for him. He will enjoy it more, and he will be tired when he gets home! and work on commands like 'HEEL' or you can also train him to 'PULL' then train him to heel. I use the pull command with my dog, and at almost 9 months he now knows that if I say heel, he is at my side, and pull means at the end of the leash digging his feet into the ground to pull as hard as he can. If I dont say anything, then he has the 6 feet of leash to be where he wants so long as he is not pulling my arm off.
THe more you walk him, the better he will get!!