1) Kohl if it's on the inside of the eye, then it's no problem because the inside of the eye is not washed during wudhu. If it's on the outside, if it's just the colour remaining then it is not a barrier however if it has mass/substance, then it is a barrier for wudhoo and must be washed off. In regards to pen marks, if it is just the colour remaining on the skin, it is not a barrier to wudhu however if it has mass/substance then it should be washed off. Ascertaining whether it would be a barrier to wudhu, based on the above law, would be on yourself.
2) The whole feet does not need to get wet. Even if the width of wiping is equal to a matchstick, it would suffice. Length of wiping is toes to ankle.