Good Morning Carla!
I can totally understand your confusion about all this, because I still have so many questions!! My son is 19 1/2 months old and up until this point had been sleeping through the night since he was 4 months old, so I know that this is a step backwards. However, I do feel that this is something we need to do in order to help him relearn how to settle in again. We've only been doing it a few days so we are in the VERY early stages of GW, after our first night of heavy crying and fighting, it did seem to get better, but I have been warned he will probably regress in a few days, so we are waiting. I also read here that when you try a new "program" to stay with it at least a week, and since you have been doing the PU/PD now for 2 weeks, maybe you should try something new?? Again I'm no expert, I'm still learning myself, I just can relate to a tired mom trying to get her LO back on track. As for the overtired part, I never even thought that about my son because he NEVER had any break downs or even acted tired... but since I've switched his schedule a little, it does seem like his naps are becoming longer... I've pushed back his nap from 11:00 to around 11:30/11:45, and just that little bit of a move, plus having lunch before his nap instead of after seems to have helped. But we still have the NW, still not sure how the GW is going to help with those, but so willing to keep on chugging along.
I don't think I answered your questions or helped, but keep your chin up, it has to get better... right?!?! LOL
Many Hugs!