Lightning Network Questions

I have a few straightforward questions about the Lightning Network that I cant really get answers on. Any clarity would be greatly appreciated.

- The BTC on the LN; how do they get there, and what is the incentive for someone to put their BTC on the LN? Doesn't it kind of go against the maxim of not your keys, not your coins?

- When people like Jack Mallers (who I love) say things like transactions on LN will cost nothing or fractions of a penny, how is that possible? What's to stop a company like Stripe to just increase fees?

- How are the transactions secure? Base layer has validations happening, whats occurring on LN to validate and safeguard a transaction?

- Are there any onboarding ramps yet, other than LN wallet apps? I know Jack spoke at length about connections to POS systems on retail, but where's the user onboarding going to come from? I'm trying to look at this from a retail PoV and see how I can get customers off of using CC's to pay for a $3 retail transaction.

- Lastly, how does LN adoption benefit the price of BTC? I see this a lot, but the correlation reasoning often seems not based on substance. Its usually fluff like, more coins moving helps the price.

Any insight would be really appreciated. I've been a big believer in Bitcoin and have struggled to find clarity on these topics as they relate to the LN.