Just off the top of my head - I don't have kids myself...but I do see you have a 15 year old - can't the oldest watch the two little ones for an hour or so while you have some "ME TIME"? Help the little ones get dressed and ready for their day each morning? And do some of the household chores as well...? (oh wait a sec, you have that as c.) I realize the 3 year old might be a bit young for most chores but certainly the other two are old enough to lend a hand - my parents had us four girls doing assigned chores by the time we were 5 years old (maybe younger but my recollection only goes back so far...)
You've got to find what works for you. There IS a balance, sometimes we need to search for it, but it's always there. For me, the lunch hour workout doesn't work, mostly because I generally don't take a lunch hour, also because I don't like to get all sweaty in the middle of the day. (almost a shame, really, because our company has a beautiful onsite fitness center that was recently renovated - Jim uses it on the weekends occasionally.)
For me, what works is getting up super early in the AM and getting my booty to the gym. It sounds a lot worse than it actually IS - I've been doing this for so long (probably, oh, about 8 years now - I started when I discovered that it was no problem getting whatever cardio machine I wanted, as long as I wanted, if I was there before most of the rest of the world showed up...

) that it's no problem whatsoever to get out of bed at 3:45 or 4:00 am.
Just some thoughts - but you have a nice list there.