1. Ramban comments on the pasuk, "V'ahavta l're'acha kamocha," that the Torah uses the term "l're'acha" as opposed to "es re'eacha" because it is impossible to literally love someone as much as oneself, as use of the preposition "es" would connote. The best one can do is admire certain traits in another person, or, as Chazal reformulate the mitzvah, not do harm to another person.
When it comes to ahavas Hashem, the Torah does use the preposition "es" -- as we say every day, "V'ahavta es Hashem Elokecha..." One's love for Hashem must equal one's love for self and even exceed it, to the point that one would even give up one's own life. (see Netziv).
2. "V'shinantam l'vanecha..." is not the mitzvah of talmud Torah -- we know there is a mitzvah of talmud Torah from other places. As the Ksva v'Kabbalah explains (he says this is pashut pshat in the parsha), the entire first perek of shema is one long elaboration of the mitzvah of ahavas Hashem. If you love something, you want to tell others about it. If you love Hashem, then you tell your children about it by teaching them Torah.
3. How can the Torah command having an emotion? You can't force someone to love? The Sefas Emes answers that love of G-d is innate. L'mashal (my analogy, not his): You don't need to command or force a mother to love her child -- there is an innate maternal bond and only a psycopath or someone who willfully tries to undo that bond can break it. (This is very similar to R' Elchanan's explanation of the mitzvah of emunah. Belief comes naturally; it is only ta'avah that gets in the way).
Am I wrong in reading the S.A. as finding an element of an issur aseh in the mitzvah of ahavah, i.e. don't undo the natual bond of love with G-d? If that is true, the parallel to "v'ahavta l're'acha kamoch" as understood by Chazal (don't do unto others...) is clear (Rashi in Mes. Shabbos writes that "re'acha" actually refers to Hashem).