Ohhhhh, you are sooo close to having that setup correctly. I currently have this exact setup for my 2 man boxing. I did not do it this way for 3 man, since the companion could be any one of the three at any point in time, depending on what my need was.

Two man is setup with (2) clickbars for each toon, and a Right click, and a Left click mouse for each bar. Total of (8) keystrokes.

Just like in my posted write up, you need to make a set of controls for healing. I like to use Big heals and Light heals. Left click does all the Light heals, and Right click does all the Big ones. I colored the bars to represent the actual toon, vs the toons companion.

The reason why you set up this in the "Control" key map is because you need all heals coming from one window, and you need to assign a hotkey to use along with the "Target Me" AND (thats the biggy.. the "and"), to use hotkeys to target the companions + using the "Target Me". Sending the ESC pre key press is the solution. You can incorporate that into the click bar control mapped key also.

If this sounds complicated, well, its because its not easy. This took Mosg and I a good half an hour to work out all the targeting. What I ended up doing, was sometimes clicking and double clicking the click bars... I do this because I need to ensure the ESC gets sent given I may need a heal NOW, vs waiting for a sorcerers casttimer to finish up.