I can't speak to spring stiffness as it sounds like you may have changed it from factory. I can say I don't find the factory ones any more difficult than other similar pistols. Though the CZ design gives you less room to grip than many other designs. Though it hasn't been an issue for me.
Regarding the take down pin, that is normal. They are very hard to push out without a tool. I usually just use the magazine baseplate as a mag is almost always handily around. Just push it with corner of that, or use something else.
