Absurd 3rd

Throughout the last 18 months of playing i've made good progress. One thing is stopping me advance however, my god darn thrid finger! The rest have good strech and independence, but the third seems to just love the company of my 2nd finger, so much in fact that making some chord shapes is very difficult (bordering impossible)
Even if i place all my fingers down into a chord that envolves a reach the finger just slides back to meet his buddy. I've tried exercises to strech them and try to keep tension in my hand to a minmum but still struggling!
I realise these fingers share a tendon or something which can make it tricky but has anyone else had this trouble, and how best did they resolve it?

I think the only feasible way is to continue practicing. What seems to help me quite a bit is the exercise shown here:



I also sometimes stretch out my hand and then touch the palm with the tip of the ring finger. Doing the same while bending the first part of the ring finger adds to the difficulty, but is a good follow-up. Initially, I used my other hand to hold back the middle finger and pinky, but I don't know if that is really good for the tendons. It helped, though, but it's probably best to take this slow. I also do an exercise where I make a fist and then lift the ring finger. At first, it lifted up barely, but after a while it went farther up (like flicking someone off, just with the ring finger).