Dies to Removal

These guidelines you are looking to build change greatly depending on the type of deck you are running, how many colors you are running, and what deck you are playing against. Which is why, in any specific case of "crunching these numbers", you should simply playtest your deck and adjust accordingly.

All I mean is that there is no "mathematically correct" number of lands; this varies for each deck, and you should just playtest extensively to get a feel for which hands you should keep against which decks, etc.

Playtesting is your most powerful tool.