I used to have horrible insomnia exactly like yours, am not a brilliant sleeper now but much much better and it is only once a week or so that I really struggle to drop off again like you.
I think all the food/drink type things help you feel chilled out before you go to bed but it's more about your own mental state, are you very stressed about work/housework/dd etc? It is a lot of responsibility... Could you be suffering a little bit of depression? I'm only going on my own experience here - my insomnia was the leftovers from quite bad PND that I never realised I had, in the end I saw a counsellor at my uni and was put on some old-fashioned anti-depressants that I took in the evening specifically to help me to sleep. It really really helped- I think lack of sleep made my mood much worse and that made me less likely to sleep, a vicious circle.
I would avoid conventional sleeping pills - they might knock you out initially but if you are very stressed you may become resistant to them and you dont' feel like you've had proper sleep anyway, there's a nasty hangover feeling that's not much better than being shattered all day.
On a more positive note, it might just be about not having a wind-down routine - if you are used to catching sleep here and there then maybe you need to train yourself like you would a baby - do it all in pretty much the same order every night. If you are doing chores, watching TV or whatever, don't go straight to bed, strictly allow yourself at least half an hour of quiet while getting washed, having a hot drink and slowly winding down. If there are things waking you up worrying you in the night, do a little journal during your half an hour to get any niggles out of your head and onto the paper.
I agree that exercise really helps, and a good dose of fresh air and sunlight every day too. Are you in an office all day?
Finally, I really do sympathise, I used to be late all the time, forgetting things constantly, losing stuff (always a sign I am not getting enough sleep) and like you say when I would settle down to do things with dd I would find I was all out of energy and also patience, which made me even more miserable. I cannot tell you how many times I lost my parking ticket and had to pay the £8 daily fee to get my car out having on ly been to uni for two hours or something! I cried at the security men so many times they must have dreaded the sight of me... Sleep deprivation does horrible things to you, especially when it's your own mind keeping you awake because you're stuck with it!