C.N.
I'm having some of the same issues myself, and am beginning to wonder if I should start cereal for her now. I can tell you what helped me with the fussy and overtired moments, though. Put him to bed earlier -- 6:00 pm! I know, it sounds crazy, and way too early, but it makes a huge difference. My daughter won't even let us put her to bed later than that, she put us on this schedule. If I start the bedtime routine around 5:30, she doesn't freak out from being overtired and overstimulated and will go down to sleep like an angel. She was sleeping until 3 and 4 am when she went to sleep at the new earlier time, then right back to sleep again until 6 or 7.
I hope for the both of us that these little ones get some more nightime sleep soon!