Valuing small private tech mHealth startup

Hey, guys!

I'm a new in VC and joined like literally 1 week ago. I'm coming from sell-side Big4 Advisory background - we did fin models for "conservative" sectors, so I have no experience with valuing young tech start-ups.
I have to submit my model in like 2 days.

Would appreciate tons if someone experienced could give some tips on:

1) discount rate - what type of unsystematic risks to consider when coming up with my rate
2) what metrics to look at
3) what to do if you're valuing a company in the market with no comparable companies - nothing, no competition, no listed companies

Anything else you can add !

Thanks tons