you just said you care about having a small main SWF.
so the option that is more logical is to have each page as a seperate SWF.
then load each seperately.
In addition, when I develop a flash website, I usually aim at it being highly dynamic,
and for it to be as SEO friendly as possible (as HTML). So a few small suggestions that are good to know in flash AS3 web development:
For loading i suggest using an AS3 library called Bulkloader (google it) which really helps in loading/cancelling/events
For the website itself, consider using SWFAddress which lets each page have its own address in the browser.
For example of the above here is the latest site i developed:
http://www.tempo-eyewear.com/
then you can enter directly inside a section using:
http://www.tempo-eyewear.com/#/products/bolero
and if you are using apache you can use mod-rewrite to have more advanced stuff, for example:
if the user enters the address without hash, you can redirect to the hashed one.
A website we developed that uses apache mod-rewrite:
www.brandcentral.me
for example if you go to the address:
http://www.brandcentral.me/industryBuzz/article0/page0
apache will redirect to
http://www.brandcentral.me/#/industryBuzz/article0/page0
and the page will load.
For Text:
I suggest you use, (if you do not already) a fonts library so you do not embed the font in every external SWF page, you just load the fonts SWF in main. the above tempo site illustrates the font loading, swf pages that have text are very small.