We only cut for behavior or supervisory concerns. For example, my throws staff (2) know how many they can safely supervise/instruct - if we get more than that, they'll eventually have a "throw-off" and some of the kids will get "cut". But they're welcome to join the other event groups, and some of them do.
We've had over 100 for the past several years. My coaching staff has ranged in size from 5-9, with a mix of full- and part-timers. I'd love to have more part-timers (there are some talented parents out there!), but it's incredibly burdensome to get volunteers cleared by the district.
Instead of considering further cuts, I think you should flip the question around and instead ask "How can I get help?" If you've got 100+ kids coming out for the team, your AD should be bending over backwards to get you what you need. Surely there's a teacher or other-season coach who could come to practice once a week and hold a stopwatch.
Next, let me see if I understand this right: with a 100 person team, you have a distance coach, and then you coach everything else? I'd suggest your distance coach has to step up and carry more of the burden. What does he do when they're on a long run? Surely there are days he could take your 400m runners into the fold, or hold a stopwatch for the sprinters while you work with another group. Distance runners are (typically) the best-behaved athletes on the team, and require the least technical instruction. Surely he can spare some bandwidth to ease your burden.
There are teams in my league with only two coaches, but none of them have 100 athletes, or cover every event group. Those that have the numbers/balance, have the coaches to cover.