50% of the puzzles I get have 2 solutions and whenever I get one wrong it's -16 and when I get one correct it's only like +5.
It is rare to find a puzzle which is "incorrect" (has more than one solution or has something else weird going on). Chances are, a puzzle may seem like it has more than one solution but actually other solutions fail or not nearly as good as the correct answer. If you don't understand a puzzle solution, I recommend opening it in the analysis and playing around. This will usually reveal why one idea works but another doesn't.
As to rating loss and gain, it is based on your puzzle rating and the rating of the puzzle. You are guaranteed a minimum +5 for a successful puzzle. If you miss a puzzle that is rated much lower than your rating, you can get hit by heavy decrease. This is by design and is similar to losing rating to a much lower-rated opponent.
15% of the puzzles I get have multiple solutions and whenever I get one wrong it's -12 and when I get one correct it's only like +10. Sometimes the puzzle is rated way lower than it is supposed to be.