1. If I wipe my head and after the wiping, I see a fibre (from clothing) can I wipe it off on my trousers or shirt and then wipe my feet?

2. If there’s something on my hands before I wipe my feet but it does not block the touching/contact between the my hands and feet, can I wipe my feet and would my wudhu be valid?

1- No need to wipe it off from your hand and if you are that by wiping it off on your trousers you will not loose the wetness from your hand then ok otherwise if by rubbing it you have more wetness on your palm then your masah will be not in order.
2- If that thing is not any liquid and very insignificant then it’s ok.