This is an exciting game and Emm and myself cant wait to play it and when its complete we will get the game we wanted :). Programming is a great godsend sometimes and others its infuriating mainly you can create anything you want and it helps you solve logic puzzles in real life, other times there is one little bug maybe a single character out or .00001 out on a value will throw the entire thing out. Implementing things like gravity into a game is another quagmire of pain and hurt to get the best results here its better to cap the velocity you fall at if you need to do LOADS of checks or do a line intersection algorithm to see if you pass through anything on your 'trip' down.
For simple games its easier to just cap velocity, games like Rick Dangerous are perfect examples as gravity plays a small part but its not 'scientific simulation' for example. There are others that do require LOADS more checks, things like Exile, Half-Life 2, The Incredible Machine where physics play a BIG part of the game and fall speeds need to increase to ludicrous levels and a check needs to be performed on it for those your best of with a line intersection so see if your object passes through another object it will tell you the exact X, Y where it took place so you can sort it accordingly.
Its all these little things that may seem trivial to a games player but to a programmer need to be thought out meticulously and cautiously after all who remembers the swinging objects in Half-Life 2 where they killed loads of things with it, wouldnt be so exciting if they just 'fell' would it. There are LOADS of physics engines out there that do this sort of thing for you, Havok is one 'popular' one and its used in loads of commercial AAA titles, to this end I am not overly worried about adding physics to Tombstone yet as there are loads of options on that front (I will leave the door open however just in case later on we need to :) ).