How do you cope with severe sleep deprivation?

[TableTime99]

I work from home. Son has been diagnosed with something which causes him to wake multiple times a night, lots of night terrors etc. He is exhausted as am I, however I have told nursery he can sleep as much as he likes and they let him sleep during the day. I'm mot able to do this as I work full time. I've been sleeping for 20 mins on my lunch break which helps a bit during the day, but I'm severely sleep deprived. I feel sick all the time. I'm really struggling. Could be months before son gets treatment. Any ideas on how to feel less tired without actually sleeping more? I often go to bed with him at 8 but still doesn't help as when I wake in the night I struggle to get back to sleep and am woken by him every hour. I'm exhausted.

Your only options are small naps whenever you can or some restorative sleep some nights.
Are you a single parent? What other support do you have?

Can you cut working hours? Can you extend the lunch time sleep? Can someone else do some nights with him?

You can't exist long term on no sleep and also work full time, IMO.

I'm a lone parent, my parents can't have him overnight and I don't know anyone else I could ask considering his sleep is so bad. I can't reduce my working hours as I'm just about scraping by. Lunch sleep can't be extended as I only get 30 min lunch break. I just feel so stuck, and I'm so tired.