I have 5 year old Parson who could be the clone of Max . And every Parson I have met is a complete headcase. They are for hunting foxes remember.
He used to succeed and wish to have a go at just about everyone but has always been OK with other dogs either ignoring them or playing with them , though I can tell he is fearful of some.
He is not rescue but did grow up in an isolated place and was never really socialised as a puppy , so when he came to me in a city he just exhibited fear aggression the whole time.
It has taken me a long time (2 years) to calm him down and get him "under control" and relaxed , but I still have to keep a very close eye on him as some people he just does not like .
At first I never let him off the lead , then only in places I could see anyone coming (like a beach) , and now I only let him off in remote areas or to play with a ball or a stick , if he is occupied he doesn't notice people so much.
His targets are random , women,men , always differently dressed etc so no behaviourist could do much as we could not reproduce the events.
All I can say is he is so strong willed I have to be without question the boss , in the early days I would have to pin him down and hold him down with a hand on his throat until he submitted , this combined with endless re assurance has made him manageable.
I never feed him before me , he is not allowed to go through a door or gate first , cross a road first etc etc, And I never let anyone give him treats.
As I live alone I don't know for you , but in some way let him know you are both the boss . I have heard Parsons are one man dogs , and mine sure hates it when I'm not around and always needs to know were I am. All I can say is forget being nice if it gets results , I used to hate getting so tough but it works and he can take it, the breeder he came from showed me this with his brother who had bitten someone , now he is OK. I would never have belied I needed to be so tough with a dog , my previous dogs just responded to good boy.
I know some other Parson owners who have resorted to shock collars , I hate them and would never , but the have had success , but more with recall problems for aggression I think it could backfire badly. After two or three sprays he just ignored spray collars.
Frugalfred sounds right on the feeding , make you both alphas?
It is worth it , well it was for us , we have a great time and he is funny,intelligent and playful . We are currently climbing in Scotland and his energy has no limits.