Hello and welcome to the forums! A solid APR is a good indicator of approval. It is always a YMMV situation with any preapproval and is never guaranteed, unfortunately. The reason your APR changed is due to federal prime rate dropping a full percentage point on 3/16; any cards with variable APR just went down a point because of this. How many new accounts have you opened in the last 24 months? Do
you have a BK on any of your reports? Have you ever had a card with Chase or with any bank they have purchased over the years?
I have a feeling you may be able to get approved for the Freedom, as it has less strict underwriting than some of their higher tier cards, but your scores are on the lower end of their approval spectrum so maybe don't get your hopes too high for a gigantic SL. Chase isn't known for dishing out SLs that are much higher (if even as high) as your current limits on your cards. You can most likely expect a double pull as well if you apply. I'm not a hardcore Chase expert, but Freedom is also next on my "to do" list so I've been doing my research too. Maybe someone with a little more Chase experience will chime in with a second opinion. Whatever you decide to do, good luck and keep us posted. Stick around the forums, too! There's a lot to be learned from a very helpful community! 
I'm in the same boat as the others in thinking your scores might be enough, but it's not a certainty. If you want to lay low for 3-6 months to see how your numbers move, it might be worth the wait.
If you do go for it, let us know how it works out. We love data points on this board!
@Remedios wrote:Chase is not too picky about scores
They do not like too many new accounts (exceeding 5 in 24 months), and relatively recent negatives.
Prequals are not guarantees, but they are very indicative of approval chances.
If you never burned Chase, go for it.
It will most likely be a double pull, TU and one other.
Good luck.
And this is exactly how I got talked into apping for my Sapphire Preferred in December even though I didn't think my scores were high enough and I had no prequal offers!
As you can see, I got the card. ;-)