Hi. I know exactly how you feel. I have also had an ileostomy due to UC about 16 years ago. I haven't had a night without a broken sleep since then. I do sleep but never in a deep sleep as I am always conscious of whether the pouch needs to be emptied. I wake constantly through the night to check it and always get up at least once.
To be fair, in the whole time I have only had a leakage in the night maybe 3 or 4 times which is pretty good in 16 years. And that was in the beginning and once when I had a blockage and then it blew out! Let's be honest when it happens it is horrible, especially when you sleep with your partner, it is quite embarrassing.
If you eat a large meal close to bedtime, it will be more likely you will need to empty your pouch in the night. On the days where I have had my large meal in the middle of the day and just a small snack at night, there is a lot less output so I can sleep a little easier. I am a side sleeper which is fine at the start of the night as I always empty before going to bed. Usually about 4 hours in, I go to the bathroom but always find it hard to get back to sleep.
Maybe setting the alarm to ensure you get up to empty your pouch would work as it would give you peace of mind. I am thinking of trying this advice myself so I can have more of a deep sleep. It is so true we cannot function properly without a good night's sleep. I am sick of being constantly tired too.
Good luck with your plan going forward :)