1) If mutual case did not go through well, can i use that video (Love making video of her & her boyfriend) to get divorce through case without giving any further maintenance as i have already given?
Yes, you can very well proceed with a regular or contested divorce case against her if she is not willing to give her consent during second motion.
You can even file a money recovery suit against her for the amount she received earlier.
2) If she is not filing any case, does her parents will file any case without her knowledge?
No, her parents cannot file any criminal case against you without her knowledge, it will not be maintainable.
3) I have sms conversation where she said that her parents threatening me only & she wants to give divorce without any issues. Does these proof would be valid?
Though the said evidence may not admissible in evidence it may be useful to corroborate hthe evidence or pleadings.
4) Can i make an additional MOU where she mention she will not file any further case or she will not ask for any monetary benefits?
You can get it mentioned in the existing MOU itself, you do not have to draft another MOU for this purpose.