What has gotten into my dog!?

I have a year old standard poodle, who usually is very calm and a good boy. But, here recently he's been acting up.

On our walks/ runs, he used to walk/ run beside me, and now he drifts his way to the middle of the street, or walks way in front of me.

He's been getting up onto the counter, when he used to not.

he's been chasing our chickens, when he was taught not to when he was young.

He's been running out the front door whenever we open it.

And he keeps causing fights with the other dogs at feeding time..

We are very good to him. There's no abuse or anything in the family or with him, and the only thing he has to hate us for is taking him to the groomers... We feed him several times a day, he gets to go on car rides.. etc. he has a perfect home. The only difference is that I stopped walking with him cause it hurts my back to tug him next to me every 30 secs. He's still sweet as far as wagging his tail at me and sleeping next to me.. Why is he getting bad?