Would taking your reactive dog to the groomers and dog boarding set it back?

I adopted dog from the city pound 2 months ago. Turns out to be reactive with growling, barking, lunging at people and especially other dogs. Didn't have any formal training yet, but have been watching youtube videos.

I have exposing him to people and other dogs at the park from a distance. When he starts to react, I have been feeding him treats. It has gradually worked to calm him.

His nails have been getting long and his fur is starting to smell. I know he doesn't like water and growls when I try to grab his paws. So instead of ruining our relationship, I took him to the groomer for nail cutting and bath. Told the groomer he was a reactive dog. They said it was okay. They had a muzzle.

Dropped him off and picked him one and a half hour later. Groomer said he was scared but did well. He wasn't mad and licked my face in the car.

Took him to the park afterwards and it seems he was set back a month. When saw other dogs, dropping food in front of him usually breaks his trance. This time, I had to rapidly put treats into his mouth to prevent him from going over threshold. He also unexpectedly viciously snapped at me that night when we got home.

In 2 weeks, I need to visit family for an overnight stay. A dog sitter at Rover . com say they will take reactive dogs. They do this full time and had other dogs in their home. I wonder how much this will set him back when I come back from my trip.