Maybe something like this, the item 1 is the second MLSTYLE, need a loop for all. I set style to 4 points then back to 2. use 0 for off.
(setq dicts (vla-get-Dictionaries (vla-get-ActiveDocument (vlax-get-acad-object))))
(setq dictObj (vla-Item dicts "acad_mleaderstyle"))
(setq dictObj (vla-Item dictobj 1)) ; second style in my test
(vla-put-MaxLeaderSegmentsPoints dictobj 2)