Knowledge in Torah is paramount.
Prior substantial experience in a yeshiva environment is key to molding both the potential Teachers mind and storehouse of knowledge which will be needed to draw upon when teaching, but his fear of heaven - Yiras Shamayim, as well which is so important in relaying and conveying Torah to students.
Practically, there are many programs, both in America as well as Israel that are geared to training future teachers or Mekarvim. Such as Ner L'elef, Ohr Lagola, Pirchei Shoshanim and a myriad of other programs.
Definitely, assuming if one has the option, to take off work for a year or two of unencumbered learning is the most beneficial, as it would allow the person the opportunity to be steeped in learning before embarking on his desired goal to teach or disseminate Torah.
You can be as successful as you much as you allow yourself to be successful. Jewish history is rife with many men who came from very parse backgrounds who created themselves and shaped themselves into the leaders of the generation בדרך שאדם רוצה לילך מוליכים אותו- The direction that man wants to go, God will facilitate you going in that direction. If you put in the requisite work needed to grow in your learning in order to spread it to others, then Hashem will help you be successful.
In terms of other responsibilities in your life, that question must be brought to a competent rabbi that you trust someone that knows you personally. This site is not the forum for such a question.
I do suggest though, to read up on the biography of the Alter of Novardohk who made a personal decision to devote his entire life to study despite the fact that he had an immense amount of family and financial responsibility. Rav Yisroel Salanter very much pushed him in when seeing his potential to give back to the Jewish people.