End of Life Prostate Cancer in Type 2 diabetic

After some advice...if anyone has any.

My father-in-law has metastatic prostate cancer and was given '3, possibly 4 months maybe significantly less' by the Oncology team back on 2nd December.  He is also a type 2 diabetic(he was put on insulin back in August/September as he had VERY high blood glucose levels, he also has Stage 4 Kidney disease, so everything combined has caused his legs to swell and made it difficult for him to get about - this resulted in a fall on Monday morning, and since then he has been in bed - we are working on getting a care package in place(we have been told today that he is now eligible for CHC and they are fast tracking it - so I'm guessing that they now think he is nearing the end), my partner has been dealing with this up until now, but he is no longer able to cope - he is an only child so it all falls to him - and I've never been in this situation so have absolutely no idea what to do to help!

My FIL's appetite was already very small, but it is getting increasingly difficult to get him to eat anything during the day - we seem to be able to get a bit of breakfast into him - but that is a very small amount, he is also drinking very little.  The doctors have stopped his evening insulin and have cut his morning dose in half, but we were still faced with a blood glucose level of just 3.8 last night - we managed to get it up to a 5, but that was with some difficulty. I'm beginning to think that it would be kinder to him to stop testing his sugar and just let him be.  I just don't know what to do for the best for both my FIL and my partner.

I hope this makes sense - Thanks