I think any marriage done with the intention of getting divorce … for what ever reason … is deemed to be haram …
I dont see any difference btw Nikkah Halaala and Nikaah mutah …
I am not clear on this issue ……. As per your statement code bhai …. If there is an Idaat for each talaq …. And yr man gives them in three instalments … aint we asking the woman to spend approximately a year in Idaat 
I think you might be referring towards Talaaqus Sunnah , in which, each of the three Talaaqs are pronounced in the consecutive three Tuhur (Woman’s Period of Cleanliness between two consecutive Menses).