Wondering if anyone has any tips to help me with my 7m/o who has suddenly turned into the hound of hades?

Tails used to be a very good dog who walked nicely always came when I called never strayed too far and ate all his food.

Over the past few weeks, I think he has started to hear the call of the wild because now he:

1) walks like a wild boar. He almost pulls my arm out of the socket. I have been doing all the basics we learned in puppy class (ie. stopping dead when he pulls...) but this just upsets him makes him whine and make monkey noises... I think part of the problem is that up until a few weeks ago, he always walked so nicely that if ever he wanted to investigate something, he would tug gently and I wouldn't have a problem with letting him go investigate, but now he swings wildly from side to side, straining at the leash (he wave a no pull harness but it does nothing) and the closer to the park we get, the worse he gets.

2) he now thinks nothing of running from one side of the park to the other and yesterday scared me to death by running out of the gate. His recall used to be solid as a rock and I have been re-enforcing since he was a baby but the time he ran away.. it was like he was in a trance.

Also, if he sees another dog... he will just go completely deaf to my calls and tear off in the direction of said creature. This worries me as there are a couple of dodgy staffies in the park with very dodgy looking owners.

3) He now just picks and plays with his breakfast. Ive tried different foods but nothing seems to work for more than 2 days in a row. He still loves treats... I think he is trying to train me to stop giving him healthy dog food and just give him a huge bowl of treats!

He is not aggressive and still loves all people and all dogs... but he has just become so... problematic!! Is this hormones?