There is just too much to fix.
Edit: I started to explain all errors but there are simply too much to explain. I can also see in the coding style that you've copied a lot code. There are some parts in the code that uses semicolon but then in the other part they're missing. also in plugin_init() it seems that you've added something later because they all aren't in order.
You're trying to get float value with get_pcvar_num when you should be using get_cvar_float (tag mismatch):
Code:
fm_set_user_gravity(id, get_pcvar_num(umbrella_gravity))
->
fm_set_user_gravity(id, get_pcvar_float(umbrella_gravity))
//----------------------------------------------------------
fm_set_user_maxspeed(id, get_pcvar_float(umbrella_speed))
->
fm_set_user_maxspeed(id, get_pcvar_float(umbrella_speed))
That fixes only 4 warnings. :/