no quick fix
I have been exercising for YEARS. I even studied Yoga for awhile.
Sorry, but there are no safe ways to attain flexibility quickly. Tolerance for pain has nothing to do with it. You will still damage your muscles. You see?
Your tolerance for pain is mental…your physical body cannot necessarily endure as much damage as you mind can.
If I stab you with a knife, you may be able to endure the pain…but your body is still damaged and bleeding. You see what I mean?
So, it is a very bad idea to spread yourself really far even if you can endure the pain…because you muscles and connective tissues are still going to get damaged. Some damage heals…some does NOT.
As far as how long it takes…actually, some of that depends on genetics. Personally, I have never been able to do the splits in my life! That is just the way the tendons and ligaments in my legs are…they are very short and tough. I COULD do the splits eventually…but it will take me a very, very long time to grow those tendons & ligaments out (like a couple of years). Other people seem to be able to scratch the back of their heads with their feet! Go figure.
As far as Jean Claude is concerned. Remember that what you saw was a movie…he was already flexible enough to do the splits BEFORE he filmed that scene! He did not GET flexible IN the movie. He is an action movie hero…just like Stallone or Schwarzenegger. The movies have to make him look unusually tough…a super hero. They put on these shows of EXTREME military type training to make him look tough. In reality, he was already able to do that stuff BEFORE the movie was made.
I would not try the rope trick.
If you tear a ligament or tendon they will heal but you could have some permenent damage. Tendons connect muscle to bone. Ligaments connect bones to each other. Ligaments are less flexible than tendons and if you tear a ligament…it might not heal all the way. You may need surgery and might lose partial movement of the limb.
The best thing for you to do is to start stretching out DAILY starting right now…and realize that you are just going to have to take your sweet time with it. It might take monts…it might take a year or two. There are no safe, quick ways to do it that I have EVER heard of.
Besides, exercise should feel good. If you are in pain you are not going to like to do it…and eventually you might get discouraged and quit. I stretch for about an hour or two. I do it so long because it like it. It makes me feel good…and now I am more flexible than I was months ago.
Take your time and enjoy it…that’s my 2 cents worth. 
“There is only ONE karate”