Just seconding the opinions of some already posted - I would ask your endo if you can switch the largest dose to the am.  When my son was younger and on a larger dose at night he also had a very tough time sleeping. He would wake up starving and drink large amounts of milk at night. He still isn't the greatest sleeper (he is 2 1/2 now) but it is much better than when he was on a larger dose at night.

The topic of largest dose in am or pm has been on this board several times in the past few years. From the "unscientific" sampling of people who post here, it seems to be a fairly even split between those who advocate the largest dose in the pm and those who say to give it in the am. The body has its largest surge of hormones in the very early am. Some doc.s say give the large pm dose to suppress the surge, others say the pm dose will have peaked prior to the am hormone surge anyway, so give the largest dose in the am. You will find people who swear by both, I would go with what works for you, your child, and your doctor.

One other thought, would your dr. consider increasing by 1/4 tab rather than 1/2 tab? 2.5mg increase seems quite a big one for a 6 month old. I know we are all stuck, at this point, with 5 mg tablets, but my son's doses have rountinely been increased/decreased by 1.25 mg and we haven't had a problem splitting the pills into quarters.

Good luck getting some sleep. It is a very tough time. I remember those awful nights only too well. At six months my son was up every hour on the hour. I truly thought I would lose my mind. It is incredibly challenging, but it does pass. I am now very glad, that even though it was very difficult, I tried very hard to respond to my son's unbelievably frequent needs for attention and food. In hindsight, his hormones were out of wack (mostly due to the liquid Cortef) and he really did need me to help him. (We did do some stuff though to try to get him to sleep better, but that is a whole other post). Try to get some rest whenever you can.