You can also use the F5-F6 keys, to cycle through some modes (but as the other user said, the engine is old, so the resolution is terribly low by modern standards, 544x416).
I'd like to do something more with him, but I am not 100% sure what form that would take. Having him interfere with the mind control content would be a little awkward from a gameplay perspective, and it would also imply he is always aware of what's going on to Erica (I figure he should only get a "warning" in case of significant bodily harm, unless he is being called by Erica). Maybe having him be more present in a few quests could improve how his role fits in the game. One thing would be to introduce some scenes with him during the main quest, so we can ask him about Erica's uncle, for example.
Gaart wasn't even in the game in the first versions, which is why he isn't fully integrated yet.