Going backwards

Kristopher's starting to go backwards again with our behavior plan. I don't know if we've started slacking and not realized it, or if he's just testing the limits all over again but it's been kind of difficult again. And I know it was just full moon recently and I swear his behavior goes crazy around that point.
The problems lately are not when it's just me, or while I'm babysitting. It's when someone else comes home, comes to visit, or we go somewhere. Anywhere that has other people and all of a sudden it's a game of showing off. While I really don't care what other people think, it's embarrassing when you have a 5 year old, who looks like he's at least 7 to strangers or people who don't know him well, starts melting down like a 2 yr old. His meltdowns are extreme. And he's 4 ft tall. I can't just easily pick him up and remove him from the room when this starts. He knows it too. And he does it with his friends around. They either decide they don't want to play with him because he's acting insane, or they copy him and get in trouble as well. Then everyone is going to start associating K with bad/trouble. Not what I want. He already doesn't have very many friends and to push the ones he does have away, isn't going to get him anywhere.
My new plan is to strictly enforce the "going away" discipline. We didn't really follow that part of the recommendations because it's incredibly inconvenient for us while we are out. The therapist told us that we need to do his typical 1,2,3 warnings and anything that would lead to a time out, instead of time out while out, we leave and go home. NO MATTER WHERE WE ARE. So if he does it when I'm almost finished with grocery shopping, I leave it sit and we go home. If we are visiting a friend and we gets to 3 or automatic time out situation, we leave on the spot. Both of those situations bother me because 1, the grocery store someone is going to have to put that whole cart of stuff away. It's an inconvenience to more than just me. And 2, visiting someone, they are stuck cleaning up whatever he was playing with there too. At least with the visiting thing, I could put him in the car seat and go back and pick up his mess quickly. They claim it will only take 1 or 2 times of this happening for him to realize we mean business. We will see....
I just want the best for him. I don't want him to lose friends and feel hurt at such a young age. I don't want him to think he's different. I want to correct all this without having to resort to meds. Which is what I'm most afraid of when school starts. They will push meds if he starts being out of control there. The behavior plan has to work and keep working. Somehow. I guess I just have to try harder.