1) I have 10m 07 and about 60m tied up in items at the moment, should a VPN be really mandatory, or can I wait till I made a few mil off a few accounts? It depends on if you are willing to risk the money you have if your accounts get banned
2) How much time does it take to manage 10 accs, 20, 50 100? For 10 accounts you should be able to handle on your own although it won't be very easy, for 20 you will probably need to get a person or 2 to help you out, 50 you will need at least 3-5 people to effectively manage the accounts, for 100 a staff of 10 is recommended. As for time, depending on how much you want to put in or how serious you are about this I would say anywhere from a few hours a day to 7+ hours per day if you have time. It all depends on the amount of accounts you want to run and if you set a target amount of gold to reach by the end of month/week/day.
3) Is woodcutting relatively good for farming? I'm running custom paths to bank in extremely remote areas (never see one person here, cutting yews), if not, what would be a better option? I personally prefer fishing for farming as you can get 1000-1400 per shark (cooked). Both woodcutting and fishing are great ways to farm gold, it is mostly up to preference. (There are also other methods i.e. combat)
4) I'm running usually about 10 hours a day per acc (with breaks enabled between those 10 hours), is that relatively safe? It honestly depends on your script, if it is made by a trustworthy and well-known scripter who has many vouches and other scripts and has a good anti-ban you should be relatively safe. Always know that there is a chance to be banned, regardless of anti-ban or not.
5) Is my IP flagged? You never know, if you have previous bans/offenses it most likely is.
6) I'm quite sure your IP isn't reset by resetting router, only resets your local IP for the router to recognize, same with a VM, it uses same IP with a different local IP for the router, can this be confirmed please? Resetting your router will reset your WAN IP if you have a dynamic IP instead of a static IP. This is not a surefire way to get off of Jagex's radar though.
7) Should I be worried about my main being banned? As long as you don't bot on it then there isn't much to worry about, you just need to make sure that Jagex doesn't affiliate you with it. If you get flagged then you should be a little more careful. (You will know you are flagged if all your accounts get banned and your new ones also get banned once you create them)
Happy botting and if you need someone to buy your gold that you farm the send me a PM on the forums or add me on Skype: niber1234567