Hi Kell, and welcome to AF,
I'm going to move this to the Ace forum, as the people there will be better placed to advise you. I'll include a few thoughts of my own, but bear in mind that I don't actually know the Ace so these will be generic thoughts.
Pre-installed apps will generally be installed as system apps. This means that you cannot remove them without "rooting" the phone (gaining administrator access, in Windows terminology - "root" is the Linux superuser account). Rooting is device-specific, so if you want to learn about this you should visit the Galaxy Ace All Things Root
Having said that, system apps are, in the devices I'm familiar with, installed on a different storage partition, so removing them does not gain space for user apps (though erasing the data for any you do not use may gain you a bit).
But if you have very few apps installed, and most of those on SD, then what you are describing sounds wrong. As a general suggestion, look at your application list sorted by size in the manage applications menu, and see which are largest. Occasionally some apps can go crazy in data usage, and app data shares space with user apps. So if you find some app is using 10s of MB of data that might mean something has gone wrong there, and cleaning that up could help with your problem.