Ivan, incredible course. In US terms, this equates to Hardrock 100 at a much lower elevation. I would approach this first year as a learning year, training and competing. Imo, you’ll want to budget more time for hiking up and running down. Flat training miles should be kept to a weekly minimum of 1 to 2x per week. The course will run much more up and down then you imagine in your “4 big blocs.” It will be constantly changing and you’ll want to train for the ascents, descents, and transitions. The dude who just came in 2nd at UTMB with a similar profile but higher elevation (if I read your profile correctly) said afterwards that he stopped worrying about mileage and started focusing on feet / meters of elevation gain and loss as his training goal. You don’t have his training base, but still, you can’t cheat the up and down. And forcing too many miles of running might not be healthy.

Don’t over-train. That’s avoidable.
If on the event day you start feeling unhealthy mechanically, stop. You can stop at 80k or 100k and still have had a massive day.
“Enjoying the moment”…hmmm…good luck with “enjoying” your first 100mile race with 30,000 feet of climbing and descending. Bonne chance!

Ivan, you might find the 16-week advanced mountain running plan (https://uphillathlete.com/training-plans/16-week-advanced-mountain-running-training-plan/) or Mike Foote’s big vert plan (https://uphillathlete.com/training-plans/20-week-big-vert-ultra-run-intermediate-advanced-training-plan/) would give you the structure you need.

With Mike Foote’s plan, you set the initial weekly distance that you run. The suggestion is 50% of your goal run (i.e. your race), and the plan then builds to 100% of your goal run, but since it sounds like you already have a pretty good aerobic base, you could start at a lower weekly mileage and build less. As hafjell noted, being able to deal with the up and down is probably going to be as important for you — including efficient technique and confidence on technical downhills.

The 16-week plan is mainly designed for people who want to do a multi-day route, but it would also give good prep for the race at a weekly training volume that might be more feasible for you.

You can extend either plan by repeating weeks — just make sure you keep the regular recovery week. That week is when the body actually makes the adaptations to the training, and it’s crucial, as you say, not to break yourself.

Jane

All you can do is train steadily, try to avoid injury and sickness so you don’t miss training volume, and see how your body recovers. IME, this will be the limiting factor. If you can recover well, you can keep pushing the mileage or hours. Your body will let you know within 24-36 hours if your biggest days are too much. I think you can responsibly train for this event with less than 200k / week. That’s more or less the distances covered by professional, sponsored athletes. How you handle the vertical gain and drop will be another issue. The problem with training for ultras is the extreme uncertainty. See Tom Evans’ UTMB. Terrific runner, impeccable training, with a lot of confidence…then on the event day, altitude, elevation, and some very fast competition changed his plans.
Your big days in the mountains on foot will be as or more valuable than the triathlon training. IME, triathletes underestimate the difficulty of being on your feet for the entire event. But you do have the advantage of long training days. These are all serious efforts. I think you’ll be fine. “North of the gr20 in Corse was 90km 8000m éelevation in 2 days, tour des glaciers de la Vanoise 70k 3800d+ in 2 days, traversée de Chartreuse 75k 4500m élevation in 12h).

Instead of ME in the next months, you’d probably be better off doing progressive 1x/week strength training (gym), with a focus on single-leg strength and balance, e.g. single-leg straight-leg deadlift on a balance disc (also known as a Romanian deadlift), box step ups; and then transition to ME once you start the structured training plan (e.g. Mike Foote’s Big Vert).

The single leg strength and improved balance and proprioception will be invaluable running through mountainous terrain, and a little muscular endurance goes a long way, so the ME that’s in the training plan will be plenty.

Rich makes very good points about fuelling. The latest episode of the UA podcast is a discussion with high-performance dietician Rebecca Dent about optimal race-fuelling strategies and nutrition for trail running: https://uphillathlete.com/podcast/training-for-trail-running-nutrition-advice-with-rd-rebecca-dent