Divorce Support Forums: need help calculating approx. support amount.

When I used the MI calculator online & approx. amounts it came up with $513 per month...but also stated that it takes no other children into account, which can be a huge factor.
I've consulted with 2 attorneys who both say that he probably won't be ordered to have an increase in support due to other children. Also since I'm the one that moved well after establishing custody/visitation, that I should be the one responsible for transportation. What I do gamble with is that he will get more than the one time per year that we settled on, which means that I'll be responsible for transportation thus costing more $$. Since moving the things we have changed have been his abatement, he doesn't take one so I get full child support even when he has N and deleting 3 of the travel times...those total save me about $2000.
Am I okay with the $600 additional per year? not really but feel like I'm in the middle of a rock and a hard place.
Luckily I can afford to not have him pay even 50%, that doesn't mean that he shouldn't however.
As far as him choosing to see N only for the 8 weeks, that is exactly what it was...a choice between spending time with his son and $$. I've known from day one that the choice would always go to $$, not that he's a bad father but he is very money motivated and has a poor work ethic. Put the two of those together and you have a poor lazy father who will take the easy road every time. Some may think badly of me for doing it, but I used that to my advantage when I chose to move out of state. I don't feel bad as he voluntarily chose to move out of state himself for a few years when our son was little and tried using him as a pawn for many years 'til he grew up himself and took at least some responsibility.

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