Is OP's goal to get a free ride JFK-LGA, or is OP's goal to get XXX-NYC-YYY?
Per the EF quote in post
#4 , MCT on DL for a JFK-LGA connection is three hours, not 2.5 hours.
My suggestion to OP is to take advantage of the now-illegal connection, and rebook (for free) the legal routing you want - and skip the JFK-LGA adventure.