The way to fulfil the most mitzvot for which you are chayev is to be a farmer in Eretz Yisrael, NOT to learn Torah full time.
Perhaps. On the other hand, the purpose of life is to do what Hashem wants, not to collect the most number of mitzvos. We know what Hashem wants from the torah, the written and oral torah. The Oral torah is transmitted through the mesorah. That is why we need to listen to our rebbeim.