Hi Jaime, sorry hear about your difficulties at the moment. I just wanted to add a few things which may be useful.
You say that your lo often wakes around 4 am - did you used to feed him at that time in the past?
It sounds really good that you are so tuned into his cues.
Looking at your routine, he has between 3.5 and 4.5 hours of naps a day. For a lo of 6 months, and I am just working on averages here, naps should be between 2.5 - 3hours during the day. At night sleep should be about 11-12 hours. It may be that he is making up for lost sleep at night (through early wakings) by having extra sleep during the day.
The other thing which I noticed, is that his first nap is quite early - I guess this is because he is up early. But sometimes what happens, is that the final part of the night time sleep cycle becomes separated appearing as the early morning nap, which should really be part of his night time sleep. You can gradually push this forward, increasing his awake time very slowly. It may help.
Some babies just have an early sleep phase, which means they always wake early no matter what you try. It's not that common, and it is good to try everything first, to make sure. Like others have said, the best way to deal with this is to adjust bedtimes so that they are earlier. Eventually they will grow out of it (as I have found with my lo).
HTH a bit