When I listen to both the real performance and the MIDI together some of the Forte notes in the MIDI rendition sound more like Fortissimo to my ears (and speakers) Those notes just seem to blare for some reason.
Are you using the full Bb trumpet library or the standard?
The best way I've heard compression explained to me is like when you're watching a movie on TV and you have to turn the volume up when there's dialogue but then imediately turn it back down as soon as the guns start shooting, explosions, space ships flying, soundtrack, etc. then turn it back up again for more dialogue. Well, in simple terms, compression does that automatically. Too much compression will make audio sound over processed or just bland and stale while too little doesn't do much of anything so the trick is to use just enough.
lImiters allow you to increase the volume of a track without affecting the dynamics and without clipping.
exciters are a type of distortion effect that add color and work great for ensembles like choirs or four part horns or something.
Delays are more useful in Pop music setttings but can add life to solo work in orchestras if used sparingly. The rule of thumb for orchestras is if you can hear the delay it's too much unless you're trying to create a dramatic effect like Goldsmith's echoing trumpets in the movie Patton .
Watch the VSL videos for the Vienna Suite and they will open your eyes (and ears) to how these tools can be used in orchestral music.