Good day my name is charitty

3 years ago I got involved with a married man with intent that he would take me as his second wife, however this did not happen, we are now separated but I have 2 children with him 3 year old and month old, he gave me a bank card so that monthly he would deposit child support money in it, he is contributing 3000 per month towards them, but the card has restriction, I can't withdraw from the card, it only swipes, and when he feels like it he blocks the card..I feel 3000 us to little for the children, as the toddler needs proper school and education, when I raise concerns he blocks card and says I should supplement because I too have a job, he earns +- 60000 a month after deduction, he pays 12000 towards his car repayments and is currently studying towards his MBA with an international University which he pays about 7000 a month towards his tuition.. Last year when he was unemployed he asked me to take out a loan in my name and he would pay it off but now he refuses to honour the verbaI agreement, I have bank statements as proof of transfer of funds, can the law help me in this regard, I pay 5700 monthly repayments in which is affecting me financially strained, leaving me unable to contribute towards their maintenance , when we separated he cancelled the lease of the apartment we were renting jointly which was the primary shelter for our children, he left us on the streets.. Now I moved back home where I am the sole breadwinner.. 

He is currently in the process of getting a divorce, with his wife and they have 3 children together, whom I feel he does more for.. Combined assets of +-2 million, do my children have any rights of benefits or can they claim in the assets of the divorce? 

What rights do my children have. 

Please advice