Since child support is based on the number of overnights, salary, insurance premiums, and few other numbers, what the custody is now compared to what it is changed to is what will make a difference. If your ex currently has every other weekend and overnights during each week then it’s likely that 50/50 custody would only be for equal time. In essence, approx. 6 more days a month than he currently has overnight.
Look over your current arrangement and see what is likely to change as far as overnights.
The only way that he would not pay child support is if you both made the same amount of money and had the children an equal amount of time. Given the difference in salary you posted, it’s unlikely that he would not have to pay at all, but it’s possible that the amount could decrease due to the difference in number of overnights.
I suggest running the calculator on the home site with equal time and see what the amount could possibly be. Not to sound too harsh, but child support is to support the child, not the parent. The courts do not care how many “toys” or assets the parents have or if the parents have to work 3 jobs to make ends meet, as long as the child/children are taken care of finacially by both parents.