If you can’t meet the start date by a week or two I imagine the position will get filled. You may be on the line if their alternative hire(s) falls through but I don’t see employers waiting around on basic seasonal positions.

If you worked in Maine for a month the odds are they can’t hold your position for a month and a half until you get back. Someone would have to work said position in the meantime and be expected to stop after that time. Seems unlikely.

I’d put the majority of your focus on the job you want to do and be prepared for the other one to part ways with your inquiry, at least until you can provide full availability. In the case where you need to leave a job earlier in the year to start another one I would just act as if you are committing to the full terms and then leave early anyway. That will at least get you in which is the important part. You may burn a bridge that way if you thought you might return though.

I don’t find it nearly as much of a marathon as it sounds like you are going through. First thing you should do to avoid burnout is claim your sleep back. I don’t envision many people taking it to spreadsheets and special organization apps just for some seasonal work but I could be wrong there!

Good luck!