You could do Frontierland and Adventureland on your half day and then Fantasyland/Tomorrowland on your full day. That’s the easiest way to split the parks. Personally, I would look at all the FP rides and pick the 6 we want to FP and then build a touring plan from that, adding on nearby rides. If there’s anything you think you might want to do twice, plan it on your first day.
You might find this post interesting - What are your must have FPPs?
ETA: The custom touring plans are great because they include the show and ‘diversion’ times so you can plan for those as well. Splitting into two days is going to be the trickiest part, because you’ll have to make 2 separate touring plans. What you put in each is personal preference.