1) All "valuations" are not created equal. Someone offers me 3x liquidation preferences, the answer is no at any valuation...
2) You don't set valuation, your investors do. If they are asking for guidance, give a big range. Or flip it around and ask them what it should be with a sincere, straight face. Ultimately you want 2 investors bidding on the same shares, and then you want to guide them to the deal you want (where valuation is just a small part of that - liquidation preferences, anti-dilution clauses, pre-investment available ESOP pool, board seats, voting rights are all part of the deal too).
3) "Pre-money" valuation is a myth and a trap. There is no such thing. Valuations are strictly post-money. Your team plus a $1? Not worth much (sorry - no offense). Your team plus $5M? Worth hopefully a lot more than $5M more, because you can put that money to use. So don't be thinking about the past - valuations are based on the future. Your team isn't inherently "worth" anything - but your team plus a market opportunity plus money in the bank to execute? Well, that's hopefully worth quite a bit. Until you have a liquidity mechanism, pre-money valuation amounts are dumb to even calculate - entrepreneurs who think they reflect the value of what they have built are generally clueless.
4) At the stage you are at, spreadsheets are a distraction. Kind of sounds like you're a spreadsheet guy with your bullet point list of different ways to calculate a valuation. Do you have someone on the team who excels at sales? Selling your shares is a sales exercise - let them lead more.
5) The investors you are speaking with have an ownership plan. Early stage investors want to own 20-30% of your company (maybe more). Later stage might be interested in as low as 10%. They will negotiate hard for this amount and often be willing to pay a lot more. Entrepreneurs instead often think in terms of wanting to raise a certain amount of money and then sell as few shares as possible (higher valuation). There is (useless) tension in these two different views - embrace your investor's viewpoint (figure it out from past investments), then try to get more cash out of them for the same percentage equity. While this drives up your valuation (making any anti-dilution clauses you agree to riskier), it also drives up the cash you have in the bank (lowering execution risk).
6) Whether it's in your nature or not, you need to be ruthless when negotiating. This doesn't mean aggressive in demeanor (be yourself) - it means you need to create demand for selling twice the shares you will sell, and then play investors off each other.
You raise money at most once a year and by yourself; investors go through this process often once a month and with a team. You can't out-negotiate them - your only hope is to have them out-negotiate each other. If you think you're going to come to terms with a professional investor based strictly on the "theory" of the value of your company, you are about to be taken to the cleaners. You're sitting down to play poker with pros and you (and I) are mere amateurs - the only true solution is to make them play each other. Say whatever you need to (including your opinion of valuation) to get 2 investors seriously interested, then let the bidding begin. Just because you say a number to get them to engage doesn't mean you're going to end up with that number.