does phosphorus and potassium help butterbeans fill out?
Yes it does! Make sure not to fertilize with any nitrogen at all, though. They "make" their own. This article will give you more information on butterbeans:https://www.gardeningknowhow.com/edible/vegetables/beans/growing-butter-beans-in-your-garden.htm
Butterbeans, aka lima beans are a cool season crop in the South. They don't like temps over 90F. They require 1-2 inches of water weekly. pH is important in butterbean growth. Ideal pH is 5.8-6.5 although 7.0 is acceptable. When pH is out of whack, plants have trouble absorbing nutrients. You need a soil test to know whether adding additional phos and potassium will help. I'm attaching an article that shows how much P, K to add depending on soil test results. You'll see that how much to add varies greatly with your baseline numbers. You are aiming for phos and potassium in high normal range. Going above normal is detrimental to yields.
DO YOU PLANT BUTTER BEANS WITH EYE UP, EYE DOWN, OR LAY THEM SIDEWAYS
Sources say plant them with the eyes facing downward, but the roots will grow downward no matter how the beans are placed in the soil.
Here's an article all about butter beans:
If I plant 2 rows of speckled butter beans, how far apart should the rows be from each other?
Your rows should be planted about 3 feet apart. Here's an article on butterbeans:
After my butter beans come up from the seed, how long before I can expect to see butterbeans on the plant?
About 70 days, or longer if the conditions aren't perfect. This article will give you more information on the care of the plant:
Live in northern Florida
According to the information below, your next opportunity for butter beans (lima) is next March.