First off sorry
I was rough. It's just I've seen some people writing some very bad stuff just because they got disapointed, and the only prob was that they didn't know what they were doing, didn't create any failsafe themes etc. and then came here bitchin' around 'cause they couldn't make it work.
Please don't hate me
And another thing, I'm not a support team member, just another user like you. So please do not blame them for my harsh words.
It would be great to have a manual as you suggested it, but so far (I used a few different forums) no-one gave them as detailed as you wrote for a free forum.
I'm just trying to help people here if I can, because I came to this forum for the same reason as you, to find answers how to do something that I couldn't figure out. I found some of the answers in the old topics and for some had to open a topic. Nevertheless I got the answers and pretty quickly I might add. So. I'm very satisfied with the forums and with the support team.
And to your problem.
To change settings in a already existing theme is a bit complicated if you don't know any html, that's true.
About the reply's letters size, it's default is small (it's in "Body (Customized in this style)" part) and for resolution 1024*768px it's great and readable (my opinion). Now to change it, you can replace it with one of these "medium, large" or just write in the value eg. 12px. Sizes in px are sizes in pixels, dots on the screen. I think that ordinary text in a forum has no need to be any larger then 12px, but it's for you to decide what to use on your own forum.
To check witch pixel size that is, you can write some text in Notepad (or if you're a Linux user Kate or some alike program) and change it's size. These programs also use pixels for sizes, so you're going to get a pretty good idea what the size of that text will be.
Hope I helped and you don't hate me
soonchica