if possible give them main meal at lunch and then lighter meal for tea. if not possible, serve something like pasta bake which you can prepare earlier, or use the oven more (sausages and stuff can be done in it, takes longer but you dont have to stand over it)
dont clear up til they have gone to bed, or the following morning. it wont kill you to have a few dirty pots around. better still, get the older kids to at least take everything away to the kitchen.
drop the bath. they dont need one every night. once a week is enough if they are small
how old is the baby? would he be ok in his car seat next to you while you are washing up? sleep training is very hard but worth it if you are willing to try. books are available in library. should get easier in less than a week.
tantrum = bedroom. ignore, ignore, ignore.
sorry if that sounds like i know everything, i really dont but these things help me get through the day!