OP I understand the situation re. that it would be hard for you to date regularly with young children if their father doesn't have them overnight (I've been a lone parent for 5 years, since mine were tiny, too).
I grew up with an abusive step father so I also understand why you'd not want to introduce an unrelated man into your children's lives. Despite what people have said on this thread - and while I'm sure lots of step fathers are great - statistically it is extremely dangerous, much more dangerous than living with their father.
However, I do not understand why you'd consider starting a relationship with your ex again. He sounds selfish and lazy, not a good parent, not motivated or ambitious, you don't love him, the children barely know him if they spend next to no time with him, what on Earth is the point? Plus you will seriously disrupt your children if you do this then leave again later.
Your posts about hating being alone, needing someone to spend the evenings with etc were very illuminating. This is what you should focus on, IMO: why you feel this need to be in a relationship. Your children are still really small, you say you work too, so you must be pretty busy! Some women jump from relationship to relationship and never learn how to be independent and feel like there is something "missing" in their life without a man and your posts scream this. It's very needy and something I'd want to address, if I was you. If I was you I'd get therapy and work on that, otherwise any relationship you form is likely to be co-dependent and have unhealthy boundaries.
My ex has no contact with my children, so if I did decide to date (given like you I would not be bringing any man into their home) the options are:
- you get childcare and go out. You say you can't afford this, so focus on career progression first? Also you say your youngest is 5 so can't have been in school for long, so presumably you now have some spare money compared to last year as no longer paying nursery costs? You can use this to go out in the evenings.
- you wait until they are older and date when they are teens and can be left alone.