Method for precise calculation? I'm tired of being stuck on a chesstempo rating 1530-1570 tactics in Blitz for like 5 days I'm "not" improving. Sometimes I  take more than 2 minutes and sometimes I just move on quickly to the next puzzle to satisfy my ego. Is there a perfect way to calculate?
Being stuck at a certain level is not unusual and I would not worry about it. 

Since you asked specifically about "precise calculation"...

You should be aware that solving tactics is not only about being able to calculate accruately many moves deep. It is also about recognizing certain patterns / tactical motifs that appear in every puzzle.

Particularly at your level it is much more likely that you fail some puzzles because you are not aware of a motif, rather than missing a defensive option many moves down the line that you did not calculate.

After you solved a puzzle or failed to do so, chesstempo shows you the motifs. Make sure you understand each of these motifs in the solution.