Hello! 720k mastery 1000+ games on Nidalee here. I suppose the first question I'd have for you is why you would choose another AP jungle over an AD jungle for your next pickup, but as someone who onetricks because I only have fun on one champion I suppose I'm in no place to judge.
1.) Best clear for invade would be bot to top 3 camp
Bold means that you Smite that camp
Start with your Q; W start is really suboptimal now because of exp changes
Starting Blue you would go Blue > Gromp > Red, Q -> E -> W
Starting Red you would go Red > Wolves > Blue, (Q -> W -> E) OR Red > Blue > Gromp (Q -> E -> W)
Here's a Reddit post by a Master-tier Nidalee player about other clears if you're interested in those:
https://www.reddit.com/r/NidaleeMains/comments/7fdme3/four_of_the_most_common_clears_you_can_do_with/
2.) You can proc the Hunt passive as many times as you're able to put the mark on something; however, Hunt marks do not stack. This means that if a target is already marked, but then steps on a trap, you would only get ONE empowered use of Q and W on that target.
3.) Yes, that is correct.
4a.) Punish junglers early with wards and your W, as well as map awareness. For example, if the opposing jungler shows up bottom lane, but you just finished clearing your Blue, as long as your lanes are in a position to follow if their laners come for you, you should go into the enemy jungle and note which camps are up, placing wards at intersections of the jungle to track when the enemy goes through there. Your W, on the other hand, should be placed in tight choke points and entrances to the jungle or directly in front of their camps, where they will have no other option but to step on them if they go to that area. If you are high enough, take the camps that are up and get out before they even have a chance to threaten you. You should also be watching buff timers constantly; they're like wards without having to go anywhere near the enemy jungle. If the enemy's blue is up soon, you know they'll likely be pathing through that way. If they show on the other side of the map a few second after their buff spawns, you know you're safe to invade and steal it without them contesting.
You should also be looking similar opportunities to take things like dragons, or especially Herald. People so often neglect Herald and spend time bot. If your bot lane can play safe and keep the jungler down there, they can easily buy you enough time to solo a Herald, even if you have to trade away one of the lesser dragons like Wind or Ocean.
4b.) Kite, kite, kite. As a ranged jungler Nidalee's inherent advantage in hear clears is her ability to kite camps much harder than melee junglers. While clearing make sure you plan your paths in advance, whether you want to gank, invade, or back afterwards. You'll also need to practice your clears a LOT. I used to spend hours upon hours making 3 minute custom after 3 minute custom practicing my clears when I first started playing Nidalee.
tl;dr-
1.) Bot to top 3 camp clear.
2.) Hunt mark doesn't stack, so you only get one of each empowered ability on each marked target.
3.) Yes.
4a.) Better map awareness for invades, ward enemy jungle with actual wards and W, pay attention to objectives.
4b.) Kite and practice.
I wish you luck and fun in learning Nidalee! She's somewhat difficult to pick up, but one of the best champions if you can really play her well. 
