It's understandable that it's touchy for you right now.
But look at it also from his perspective; he feels you watching him, looking out for him putting a foot wrong, and the reactions to his mistakes in behaviour are so out of proportion that he becomes extra tense, and then tries to avoid the tension and confrontation by lying, which makes it worse, which makes you even more tense and vigilant, which makes him more tense and avoidant...
It sounds like a bit of a time bomb.
I wonder if it might be useful for you to decide on some clear criteria about lies to have at your own disposal – what size or nature of lie is actually unacceptable (and why) and which are little-boy lies that you can roll your eyes at and smile (and why).
You could base your choices on the consequences of the lies, for example...
Extra piece of chewing gum = not hurting anyone, you're not going to explode for lack of chewing gum, let it slide.
Said he was at friend's house, was actually playing in the street = dangerous, meaningfully erodes your trust = don't let it slide.
It sounds like you're pinging off any old trigger, so some thoughtful decisions and clear criteria could be a useful tool for you.
It'll help him understand where the boundaries are, too.