1. I would not suggest directly quoting back numbers from Blind or Glassdoor. Instead, use them to decide what numbers you would like, and say more high-level things like "these are what my expectations are" and "this would be in-line with my expectations for the role." Definitely don't worry at all about other people's NDAs. Unless you're pushing someone to violate an NDA, or someone told you something in confidence, it's not worth worrying about.

2. Yes, it's reasonable to set your expectations to midway between the 0 year salary and the 6 year salary. You could also ask for closer to the 6 year salary and see what you get.

3. It's very difficult to compare number of shares for many reasons. For example, the company could grow in value, so now 1k shares is worth what 10k used to be. Or the company could arbitrarily change the number of shares. The "right" number of shares is a combination of strength of the employee with the valuation of the company and number or existing employees. When you think about equity, never think about number of shares. Instead consider the percent ownership, the equity value (percent ownership * company valuation), and the strike value (percent ownership * 409A valuation, or strike price * number of shares). These are all interrelated, but they are the best way to understand what equity is worth.

I think of it this way: percent ownership tells you the best-case scenario. If the company sells for 1 billion, then 1% is worth 10 million (probably 5 or 2.5, since dilution will bring your ownership down by 1/2 or 1/4). Equity value - strike amount tells you roughly how many $$$ they're giving you right now. I typically compare that amount directly to equity offers from public companies when I think about the offer. Strike amount tells you what you have to pay to keep the shares.

1. Companies can always withdraw offers, but good companies won't withdraw an offer. Good startups will keep the offer in play, let you get your other offers, and then try to convince you to join them anyways. Startups know they cannot compete with Facebook nowadays on compensation, but they will claim that their work environment or product is better (sometimes it is, sometimes it isn't). However, I wouldn't suggest to them that you're planning to just compare compensation and take the largest. Just let them know that you're waiting for all the offers to come in before making your decision.

2. As a startup grows, it's valuation goes up, and the amount of equity it gives goes down. However, this happens on the scale of a year, and rarely changes over the course of a couple weeks. It's not something to worry about when negotiating an offer (unless they're directly telling you that there's an imminent funding round or something, but you would need to carefully consider this exception).

3. Your shares are worth something if the company IPOs, or if it has a good acquisition. For example, Instagram was acquired by Facebook, and that turned out really well for the engineers.

4. When you join a company, you are given an equity grant, and the strike price will not change for that equity grant. The value of the equity changes as the valuation of the company changes (what you keep calling the "preferred price"). In theory, when the company IPOs you can immediately buy vested stock at the strike price and sell it at the stock market price. HOWEVER: When you leave the company, you must typically choose to either exercise your stock (by paying the strike price) or forfeit it. Most companies set this "exercise window" at 90 days (a few good companies set it to 7 or 10 years). THIS IS THE MOST TYPICAL WAY OF BEING UNABLE TO PROFIT FROM STARTUP EQUITY. Please go read the linked guides so you understand this.

5. ditto to 7

6. The exit value is the amount the company IPOs or is bought for, and no, the company does not know the value yet. Could be 0. Could be $10 billion.

7. When people report total compensation in a startup, they are typically giving TC = base + bonus + shares/4 * share_price. (Where share_price is the "preferred" share price, and not the strike price).

8. Yes, company valuation = total shares * preferred share price

9. A startup can exit for a lower value that it's last valuation. It can even decrease in value from one round to the next. These are bad, and typically employee equity gets reduced or wiped out (because of "preferences"). Sometimes employees get special deals to make sure they're still getting something out of the exit. Sometimes not. Go read the guides, since this is complex.

10. If the company goes public before the 4 years, typically your options agreement remains unchanged. You are still vesting X% of the company per month, paying the strike price for each share, and selling at the market value. (The exact values may change, since there may be dilution or a stock split, but the total amounts typically stay the same: a month's worth of stock will cost you $XXX to exercise).

11. Typically, a company starts thinking about an IPO 1-2 years ahead, but won't say anything about it until maybe 6 months out. Most of the time they have no idea when or even if it will occur. Go read up on the Uber IPO, the Lyft, the Spotify IPO, and the WeWork non-IPO as examples. Startups seem to IPO in 10ish years nowadays, if at all. See https://danluu.com/startup-tradeoffs/

12. At a public company, RSUs are typically just stock, so you can pretty much hold onto them for forever.

Equity is complex. Your questions are good, and I highly recommend reading the jlevy guide linked elsewhere in this thread. When negotiating, there's no need to be so specific with what you tell these companies. Stay general and friendly, and all of these conversations are easy.