The "maximum file size" is dependent on the hardware and software it runs on. That said, the only Twine game I know of that started to hit those limits was almost 83 MB in size (primarily through embedded images, which isn't recommended for this very reason). Since you're at about one 166th the size of that, I'd say you're probably safe.
Also, the amount of branching or passages doesn't really slow the published game down, though it may slow down your ability to develop in Twine itself. If you start hitting enough passages that editing in Twine becomes cumbersome, then it might be a good idea to switch to using Tweego as a command line compiler of Twee source. Tweego can turn existing Twine HTML into Twee source, and then you'd use an editor like Notepad++ or Visual Studio Code to edit it, instead of Twine, and then Tweego could compile that Twee source back into HTML.
What can slow the game down would be having a large number of story variables (variables that start with "$") and a long game history. This would become noticeable as slow transitions between passages, and slow loading and saving times.
The best things to do to avoid that is:
- use temporary variables when possible (variables that start with "_"),
- store data which gets set at initialization and never changes on the setup object instead of using a story variable (e.g. in the "StoryInit" passage you might have "<<set setup.maxitems = 20>>", assuming that number never changes),
- try to avoid storing redundant or unnecessary data in story variables,
- and use the <<unset>> macro on a story variable when you're done using it.
Hope that helps! :-)
 Tweego: http://www.motoslave.net/tweego/
 Notepad++: https://notepad-plus-plus.org/
 Visual Studio Code: https://code.visualstudio.com/
 setup object: http://www.motoslave.net/sugarcube/2/docs/#special-variable-setup
 <<unset>> macro: http://www.motoslave.net/sugarcube/2/docs/#macros-macro-unset
 Config.history.maxStates: http://www.motoslave.net/sugarcube/2/docs/#config-api-property-history-maxstates