So here's my question, if I file a request for modification, will the court use the 'old, grandfathered' rules that were in place at the time of my divorce, or will my modification request result in 'all new' calculations using the current methodology?
No grandfathering of rules, your modification will follow the new rules. I know this because I had a similar question to my lawyer, about a year ago.
Both you and I were lucky to get divorced in 2014. Based on the new maintenance rules, both you and I, for a 17 yr marriage, would have been forced to pay alimony for 13.6 years ... a heck of a lot more than the 4.5 yrs or 5 yrs you and I settled for.