I watched the video, and overall liked it. Since you asked for feedback: with the video format, I think I would prefer to see the question and be told to pause to have time to think of the answer before it appears instead of having a set amount of time for each question, since with at least some of them you either know it or you don't right off the bat. As it is, I got a little annoyed waiting a minute for the answer if I already knew it.
The other main comment is something DejMar sort of alluded to, that there are potentially multiple answers that would make sense for some of the riddles. In particular the second one, I also interpreted it as most likely being a gotcha where each number in the sequence is (n)/(n+1), so the final term x/1000 comes after 9/10 and should equal 10/11, meaning x = 10 x 1000 / 11. Only after realizing that it wouldn't be an integer did I decide that it probably wasn't what you intended to ask, so the answer should be the other thing I had in mind and be x = 999. With the light switch, when I saw it here I thought there must be three positions with something like "off" going to "medium", "medium" going either to "off" or to "high", and "high" going only to "medium" so there would be a unique answer -- after any even number of flips the switch must be back at "medium" -- whereas with the youtube version if you change directions during flipping you could either end up at the original position or 180 degrees away. For the question of painting 8s, I could have interpreted a couple of ways: you could argue that he would only paint 8 once (if it's referring to house number 8, or just the number 8 and not other numbers that happen to have 8 as a digit), that he would paint it 20 times (if you mean the total number of digits that are 8), or maybe even 19 times (if you mean the total number of houses with any 8 on them, although that's a less likely interpretation). DejMar commented on the ambiguity of whether the question with Little Johnny is talking about making it home with the original $300 dollars or the money that the man is offering, but I suppose that ambiguity needs to be present or else it wouldn't be much of a riddle. And the last question seems like it might be a bit offensive if asked to a woman.
It might not be possible to make the questions entirely unambiguous, especially the question about Little Johnny since the ambiguity is what makes it a riddle in the first place, but sometimes simple things like saying "how many times does he have to paint the digit 8" can help make it unambiguous. In general, I would say to check for (and ask other people to check for) unintended ways that the questions might be interpreted.