Duong I don't get your first point. Could u reexplain this story of "optional result"?
in the ranking points of a player there are normally 18 mandatory results : 4 slams + 8 mandatory Masters 1000 tournaments (MonteCarlo is optional) + 6 "optional results", that is results got in other tournaments which are optional, like ATP500 or ATP250 tournaments or challengers or futures or Davis cup or Monte-Carlo.
But for players whose ranking is not high enough to enter directly in a mandatory Masters 1000 tournament (or a grand slam), if they don't play that Masters 1000 tournament, they can count 1 more optional result for every Masters 1000 tournament they miss.
Monfils is in that case for Indian Wells and Miami of a player whose ranking is not high enough to enter directly
into the main draw (he's only an alternate), that is in the case of a player who can count one more optional result if he doesn't play that tournament in the end. If he finally got in as an alternate or a wild-card or a qualifier, he would have to give up this supplementary optional result.
He already got one more optional result because his ranking was not high enough to enter Paris-Bercy, that is he theoretically already can count 7 optional results instead of 6.
But Monfils's problem is that instead of 7 optional results, he only can count 3 of them at the moment because of another rule which says that a top-30 player has to play 4 ATP500 tournaments in a calendar year, whereas Monfils couldn't play any of them last year because of his injury. And this has the stupid consequence that those 4 ATP500 results that he should have played are replaced by 4 "zero point" which he will not be able to replace with a not-null result until july (2 of them) and october (2 of them).
The consequence is that Monfils can only count 7-4=3 optional results from ATP500 and ATP250 tournaments at the moment. Which has the consequence at the moment that he can't count his 45 points from Bangklok and his 20 points from Montpellier. And his points from Rotterdam and MArseilles will only count if they are superior to 45 points.
If he skips Indian Wells and Miami, he will be able to count 2 more optional results (that is minimum 65 points = 45 from Bangkok and 20 from Montpellier, more if he does better in Rotterdam and Marseilles).
Of course he could have hoped to make even better in Indian Wells and Miami, but considering the ranking advantage to skip those tournaments I just said, and the rest which might be useful to prepare clay season (and maybe the Davis cup tie first), I think it's not stupid at all to make the choice of just not going to play in the USA.