Targeting a profitable niche - question

Hi there.

I'm up to start an online information business and I'm in the process of finding and targeting a niche.

I've been through some Eben Pagan's (an Internet marketing expert) materials and there is said that in order to target a profitable niche 4 components need to be right in place.

1. Does the customer experience pain or urgency to solve its problem?
2. Is the customer pro-actively looking for solution to his problem ?
3. Does the customer has few or no other perceived options ?
4. Are there at least 1 in 1000 people that fit in the group of my prospective customer ?

So my concern in for the last two.

How do you figure out if there are few or no other option on the market for the current problem. Does not having a book on the topic is enough to indicate that there is potential for an unmet niche? What other tactics could be allied to figure this out ?

And how do you figure out if there are at least 1 in 1000 people that fit for the niche ?

I do Google Keywords research with the keyword planner to see how much people look for the problem they have. but I don't know if lets say 1900 people have looked for this month
for "natural stress relief" is that enough so an product be created around that.
(note this is just an example)

What other methods do you use to determine that the niche will be profitable and the need exists in enough customers that are able to pay?

cheers.