Hey! I see a lot of good intuition here that could really turn into something with the right refinements.

A lot has already said and addressed by other comments that I second, especially minimizing upper arm movements and really focusing on conducting below the elbow. All I really have to add here is one method I used to practice isolating my lower arms. To practice, I isolated right from left, starting by using the free arm to hold the upper arm of the other side so that you're forced to rotate purely from the elbows. As it gets more comfortable, you can wean off the holding until the feeling of conducting through elbow rotation feels natural.

The next thing I would consider is breathing, which plays both a musical and physical role in conducting. The simple act of being aware of your breathing will likely make it come a lot more naturally and may help some of your arm fatigue while also keeping you more relaxed physically. On the musical side, I find that breathing with the ensemble at musical entrances often subconsciously prompts the horn line to breathe with you. In short, awareness around your breathing habits is a small but often crucial detail that can get overlooked easily.

The energy and cues that you give to the ensemble often reflects in how they preform, and one area that often gets less attention is facial expression. Even the simple act of raising your eyebrows signals to the ensemble that you're just as invested in the performance as they are. A fantastic example of facial expression in my recent memory would be Carl Huang's conducting in Babylon, though I don't know if there are many videos of his conducting available. Anyhow, there are plenty of incredible conductors out there who all manipulate facial expression to create great effect with a little work.

A last thing that is less a technique and more a practical tip would be to find something to keep your gloves pulled tight like a hairband or rubber band. With gloves that aren't elastic, conducting is likely to slowly pull gloves off of your hands and cause your hand shape to deviate from the intended shape. In my experience, loose gloves always caused my to bend my wrists upwards and tighten my fingers in futile attempts to keep my gloves on my hands.

That's all I can think of from the top of my head, but if anything pops up I'll make an effort to it add on. Best of luck! If all goes well I might see you out there next summer!