I need 20 to 25k a month and I'll settle.
No you don't. You are separated and have a boyfriend to help contribute to your livelihood, between the 2 of your salaries, you should be able to manage putting a roof over your heads, food on the table, clothes on your backs, and other miscellaneous expenditures within your budget. Note: Within the budget of your new reality, not former life with rich husband. You qualify for offset CS and a period of SS based on the duration of your marriage.
You do not need $25,000 per month. You would like it, but don't need it.
99% of people would bend over backwards for $5,000 per month. You can rent a nice place in Toronto for $3,500/month. And you have $1,500 leftover? Wow! That is great. That is more than enough for clothes and kids' share of food consumption. So it looks like your ex will continue to provide you with free housing.... must be nice.
with 50% section 7 expenses split 50/50. The kids section 7 expenses are close to 200k a year.
Actually, section 7 expenditures are supposed to be split proportionate to your incomes. In your case, it would be that your ex pays like 90% of the expenditures. So if your kids dance class costs $500, he would pay $450 and you pay $50.
There is no way in heck that section 7 expenditures are $200k per year. If it is, it is completely uncalled for and can easily be scaled back. Either way, see my previous comment about it being proportionate to salary.