Am I being unfair (my ex thinks I am)

My ex and I broke up early 2021.

Tdlr;

We were together 7 years. I had 3 other children prior to meeting him. He took on my twins as his own (their father has never been involved), and we had a bio daughter in 2017.

I have provided everything for all kids.

I owned a house from 2007 until end of 2019 when I said I was looking to buy another home. At this point it was without him because he was always half in/half out. Even when he lived at my place from 2017, he never paid a bill or helped with anything, not even his own kid. I was at the shit or get off the pot point and moving on with my life with or without him. He said why don't we buy one together, I'm ready. I asked at lwast 100x if he was sure. He was. We bought a house.

From he time the pandemic hit until we broke up he was "working" 12 hour days while I worked from home, was mom, dad, maid, cook, etc. He was never home, claiming he had to work. Turns out he wasn't even working his regular hours and lying to me in order to go to his moms vacant apartment to jerk off and smoke pot all day. Not giving a flying fuck about myself and our kids. I mean, I literally, in tears begged him to come home because I was beyond burnt out. This went on for 18 mths, and while his paychecks never added up, I paid for fucking everything. When I found shit out, he forced me to sell the house.

Well, we have a separation agreement that I gave him a week before signing saying he would pay $500 in child support and half section 7 expenses (daycare, extra curricular, etc.). He signed it.

Well, he gave me a lump sum for daycare and child support with it to resume in January.

I have received the child support $500/mth for our bio kid. He doesn't pay anything for the twins.

I calculated our kids portion of daycare, which totals $300/mth. He is refusing to pay his $150 portion.

I paid Jan and Feb, and he said he would only give me $100. I'm fed up. I'm fed up with the responsibility of the child he wanted to always fall on me. He literally takes the kids 4 days a month or 13%. Has the audacity to tell me that daycare is because I need it and he shouldn't have to pay it. Says that before and after care isn't daycare so isn't his responsibility.

He keeps telling me to take him to court, which is ridiculous just for a judge to say the same shit. However, I just wonder if I'm being unreasonable making him pay for child support (which is the table amt in my province and covers basic needs), plus daycare which is an extraordinary expense.

Total:$650/mth.

He is terrible with money, and he got 60k from the sale of the house (that he paid nothing into I may add), he is a complete pot head and pays a lit more than 150 a mth on pot. Smokes, and a pack is about $16. He's paying rent at a place he only goes 4 days a month because he rather stay at his moms apartment. He is paying $250/mth for a storage unit his friend has offered to help clean out for the last 6 months.

I guess I just don't understand. I don't feel like I'm being an asshole, but damn.