Everybody has problems with their pinkies when playing guitar, at least early on. That's due in large part, I believe, to having grown up in an age of automation that's obsessed with maximizing convenience. Consequently, we've effectively stopped using our pinkies in a dedicated fashion. It's just along for the ride.
So, at some point, every guitarist needs to strengthen and train their fretting hand pinky finger to do useful tasks for the first time. Those spider walking exercises fit the bill nicely, as would playing chords that require the pinky (especially those that require reaching with the pinky). Realize however that it will probably take at least a few months of daily exercises to start perceiving any improvement. Even longer for "vintage" model guitarists like me ; )
So, patience and practice. That will eventually get you to where you want to go.
"Whatever you are, be a good one" - Abraham Lincoln