What are specific usage of: "very much", "so much" and "too much"?
This question could almost be closed as "too broad," but I'm going to take a stab at it. Just realize that my answer may not be 100% complete; these are versatile phrases that can be used in many ways.
I'm going so say that "very much" and "too much" (usually) mean two different things, and that "so much" can be a synonym for either one of them, depending on the context and the structure of the sentence.
I would say that, in general, too much means "more than the right amount," while very much means "a lot, but not necessarily to excess."
Linda loves Bill very much.
means she loves Bill a lot, while:
Linda loves Bill too much.
means she loves Bill more than she should. (Perhaps Linda is a lovestruck teenager with an unhealthy degree of infatuation, or maybe Bill is a celebrity, and Linda is a stalker.)
Given that, I would say that:
Linda loves Bill so much.
is generally synonymous with the first sentence (i.e., it's saying she loves him very much), not the second sentence (i.e., it's probably not saying that she loves him too much). That said, it could take on the meaning of the second sentence if we add a little more context to make it that way:
Linda loves Bill so much it isn't good for her.
Another example, where these phrases are used in the negative:
Don't put very much cinnamon in the coffee cake.
means only put in a little bit, while
Don't put too much cinnamon in the coffee cake.
means only put in the amount that is required (it might be a lot), but not more than that. In this case:
Don't put so much cinnamon in the coffee cake.
is probably more closely aligned with too much cinnamon than with very much cinnamon. Again, though, it's hard to dissect the meaning of such simple sentences, because the same words can be used to convey different meanings with additional context. For example, if we are making the coffee cake, and I say:
Don't put so much cinnamon in the coffee cake! You'll ruin it.
that means: "Stop putting cinnamon in the coffee cake right now!" (That's enough cinnamon; any more than that will ruin the cake.)
However, if we are eating the coffee cake, and I say:
Don't put so much cinnamon in the coffee cake next time.
that means, "Next time you make coffee cake, use less cinnamon than you did this time." (There is too much cinnamon in this.)