As an EP practitioner you often find yourself in a crowd being jostled and shoved as people try and get around your protectee. When I first left the USSS, I was still a fairly thin little guy, and working in such small teams, and even alone at times, it left me getting moved off position at times.
We developed a balance training program, that just grew, as more legal issues became a problem.
Take a heavy bag - I used a 4 foot long 80 pounder - and mount it from the ceiling to where the bottom is around your knees. Now start by just standing under the bag, so the chain would be coming down thru the center of your head. Now just try turning and shifting your weight, yet retain your balance, and stay directly under the bag. With a little practice your body will start making adjustments to handle the weight. If you have others around you may want to ask them to gently pull the bag back and let it fall into your space. This will help you take the weight, like a shove, and learn to regain balance quickly.
Now for the legal issues, it seems that when we get into legal trouble it is like getting a foul in basket ball. When you open your arms to grab or shove people, that is the foul. So try keeping your hands tucked in, you may want to start by grabbing your shirt, this prevents elbow throwing to a great extent, another foul, or in your case legal issue. Practice standing your ground, then practice moving in and out of the bag's center area.
After a little time this also becomes more of a second nature, and you do not have to think about it, or go into some defensive stance.