Don't know what kinds of hills you deal with out in bluegrass country but, yeah, hills make the difference between a suffer-fest and a fun century ride. I'm just trying to get back into a relatively faster flat century this year and then take on a hillier one next year. Since I don't have a cycle computer, Carmichael's book probably wouldn't be useful but I'm hoping my winter dumbbell routine will help my knees for the hills.
And I'm trying to work around an even more restrictive time schedule than the OP since I work the second shift. So I'll have to make my short Wednesday ride an interval one rather than just pushing a heavier gear than I do on my weekends. Hoping the squats and intervals allow me a to maintain a little more power on my longer rides.
Also will have the luxury of sub 40 gear inches on my old bike this year with a new gearing setup. We'll see how that helps on the hills. Plan to be be using this winter's build for my flatter Wednesday wind-sprint rides.
If I try to get too ambitious too fast, after the decade layoff and on limited time, it kinda takes the fun out of it as well as risking overdoing it.