I separated from my STBXH last April, (some of you may remember my thread - about my parents disowning me etc because I left H because I was so unhappy) although we had to continue living together until September, due to work commitments, selling the house etc. Since then, I have resided with the DC in a rented home and he moved back home to his parents. He took 65% of the sale proceeds to the house because I earn more than him, although at the time he earnt a fair wage.
He then got sacked from his job for stealing, and now works temping at a firm, earning a fair amount less. He gives me 200 a month (he earns about 1000 a month) which equates to 100 being half of a joint loan we still have outstanding and 100 a month towards the DC. He also pays 20 a week during school term for the breakfast club.
So as well as living expenses and rent on my home with DC, I also pay 400 a month for the after-school club, with no assistance from him, I have no money left at the end of the month and struggle, but we are happy. He collects DC at 5pm and spends time with them til I get home to collect them between 6.30 and 7pm. He gets more quality time with them during the week, then I have one day a weekend where it is just me and the DC, then the other day he spends half the day, or has them for a sleepover, although this has only happened 4 times in the last six months.
All seemed to be going OK, but he has now found out I am seeing someone. He has now threatened to quit his job and go for custody and I pay him maintenance. It terrifies me that he could even consider this an option. I have always fully encouraged joint custody of the DC, I understand he is short of space at the parents, but I try and encourage sleepovers as often as possible, although he has thus far cancelled one sleepover so he could go fishing [sceptical]
Before we split I worked evenings, so spent all day with the DC, doing school runs, doing everything at home etc. I considered myself to be primary carer, then he would look after them when I went to work, which would total about 2 hours a night before they went to bed. He did nothing for them, he hadn't even taken them to the park on his own until we split up. I encourage them to spend as much time as possible with their dad, I do all the running about dropping them off to him and picking them back up again. He cited my unreasonable behaviour in our divorce, due to my working evenings, made him feel like HE was the main carer. I came home on many occasions to find him drunk!
Please put my mind at rest - surely at most he would be granted joint custody? DC are 8 and 4 and so far seem happy, they get a good quality time with us both, both doing great at school. They are my absolute world and it terrifies me that a judge would even consider granting him custody just because I work fulltime, something that hundreds of thousands of parents have to do 
I know he is probably just saying this because I am now seeing someone, but I just want to be able to ignore his silly comments and continue trying to be the best mum I can possibly be.