How Many "Functions" Fit into a Macro?

I am pretty new to the VBA side of Excel, but understand how to record my own basic macro. I have a sheet in which I need to change the value of one column to something else completely. Right now, I am using a basic find and replace function (right word?) to do this. However, the project is hundreds of these functions. So my question is how many of these functions/lines can fit into a macro before it is no longer functioning? It seems that once I get passed a certain number it stops to function - but due to the high volume of entries the exact number is hard to track down. I am just trying to get a basic idea so that I can reset these macros and be sure they run correctly. I cannot seem to find an answer to this online.

I am attaching a sheet with the picture of just a small bit of the macro to understand what is in it, plus the same code just copied into the word document. As I learn more, I'd like to obviously know if there is a way in which to do this without adding a bunch of macros to run everything. If someone can just point me in the direction to learn that information, I would be grateful.

Thanks in advance!
Jen