I did the ST using ACA ST maps, but deviated from them where it made sense to me. I found that I reduced the distance a good bit and didn't feel like I missed much. Oddly enough I met as many or more other riders when I was off of the ACA route as when I was on it.
Personally in the West, I don't mind riding the interstate more than the ACA suggested. For as far as it goes I'd be inclined to ride US 90 much of the way. I made most of the route decisions on the road as I went and would do the same again.
You will find that the ST is a good route for knocking out long mileage days, so 5 weeks isn't a slam dunk, but is possible. I went W-E and stopped in Pensacola, but if I had gone all the way to St Augustine, it would have taken me 5-1/2 weeks or just a bit less. To calibrate that, I was 61 and not especially that fit starting out. I do tend to like to do long days and not take rest days though. I think that if I started out in real good riding for and wanted to I could finish in 5 weeks using mostly the ACA ST.
I went in Feb.-Mar. so the daylight hours were longer for me. Personally I think that is a better time to go if your schedule is flexible. I also went W-E. I think the W-E direction makes sense if you think you may run out of time because it is pretty easy to cut the route shorter without missing much. Also if you make it to the gulf, it is a coast to coast trip even if you stop there. That worked out well for me because I have a daughter on the Florida pan handle, so it was nice to finish there.
BTW, I am now living in Tallahassee, so if you need a place to spend a night there look me up.