At the beginning I want to say that most of it is in the game. As far as tackles and the equation you use, I don't think they tell the whole story. "Tackles Won Ratio" is the best stat here compared to "Tackles Attempted per 90 mins".
Also for number 4 can you give me an example? Because usually the "per 90 mins" stats are small and in decimal format, while the playing minutes are in the hundreds or even thousands. So for example if we have a number for the first one e.g. 2,3 GAA/90 and 1000 minutes of playing minutes then the result would be 0,0023.
A more correct formula here would be to do the total goals conceded by the goalkeeper by dividing them by the amount of playing minutes and then multiplying the number by 90.
For example: (80 goals allowed / 2500 playing minutes) * 90 = 2,88 per 90 mins