Your vet might give you a dose of Stresnil for him (it's an injectable sedative) which will calm him down and make the job easier

Even if you have a buy a whole bottle it would still work out cheaper than his prices

As for whether he'll continue to see you as a threat or hold a grudge, I doubt it - he was just getting you away from his ladies. As long as you give him plenty of space around the time when they're in season and he's active you should be fine.
Our Kunekune boar is a soppy thing - loves a good scratch and belly rub, but if there are gilts or sows in season you can see him 'treading' the ground when you go into the pen, it's just his way of letting you know he's the boss

He goes back to normal once the hormones have subsided.
You were
very lucky - always take a board in when you're in with a boar

Hope you're right as rain soon,
Karen