YMMV, but my gut reaction to your five points is:

1a) Why do you want it to be paper? And do you mean paper only? If so, my view is that you'd be looking at much lower revenue than if you were open to ebook versions (instead or as well). Don't overrate the prestige of paper these days. I'd rather 10,000 Kindle/PDF readers over 1000 paper-book readers.

1b) I've not dealt directly with traditional/print publishers as an on-the-books author (have never found a commission that pays enough to make the time+deadline worthwhile), but experience from dealing with them as a journalist (my previous life) is that there can be some really great people out there at publishers, but you need to find a good 'personality' match between you and the firm. What publishers whose books you have read seem most closely aligned with where your book is "at", culturally? If you can't think of any publishers because you haven't read any such books, get reading. If you can't think of any because there doesn't feel like there's a match, you've got a tougher challenge on your hands - self publishing may be the way forward.

2) The lack of a track record will make it harder to get publisher attention. Not impossible, but definitely harder. (This is partly why self-publishing is rising in popularity.) You'll need at least a couple of representative sample chapters and a solid synopsis of where this is going for them to get an idea of whether you're a) saying something worth reading and b) capable of expressing it well enough to work as a book. If you've got some kind of pedigree/relevant background/expertise/credibility that will help a lot, but only if you can write well. It may sound cynical, but these are all factors that help mitigate the publisher's risk in taking you on, and that's what really decides whether something gets published or not.

You'll also have to see whether the publisher you have in mind accepts unsolicited submissions. Not all of them do.

3) "Will such interviews be difficult for a first-time writer?" Have you interviewed anyone at all before? If not, practise on friends/family, interviewing them about anything (don't worry about writing/recording - just get used to the interplay.) Experience really helps you think on your feet and change what could be a pro-forma Q&A into a proper, interesting, interview. Doing it on the phone is good for that natural flow, but doing it over email may also work, depending on your question set and how you're planning to write it up.

If you're doing it over the phone, record it and transcribe it fully before writing it up. Keep the recordings and that paper record safe. They are your defence if someone challenges what you've written about them. Decide ahead whether you're going to let your interviewees read the resulting copy -- you don't have to, but for this kind of book I think it could be good to avoid inadvertent altered meanings during the write-up and the related fallout, if you're new to this.

4) Finding an independent editor is basically hiring a freelancer - lots of options if you google, variable quality unless you're careful [or lucky]. Look at how much money you think you might make from the book (depending on how you choose to publish), then halve that (because every writer over-estimates how much they'll really make) and then see how much of that you want to hand over to an editor, if you can still afford one.

You can save yourself some cash by doing as much prep and polish as you can: plan ahead for the structure of your book and its sections, get real friends to read it (not your parents - you need someone totally objective) and suggest changes. Be structured in your 'bug tracking' and keep polishing up to a pre-set number of revisions (else you'll go insane). If someone says your book is truly perfect, they're lying. But at least they're being nice.

5) I've bought 30-page things that call themselves books. I've also got a 600+ page hardback sitting here, waiting to be read. Don't sweat the number of words - focus on making whatever you're writing as useful and engaging as possible.

And, along with what danso says about writing a blog to get you started (which sounds like v good advice for someone who sounds relatively inexperienced in all this), check out leanpub.com, which is the most friction-free way to publish I've yet come across, with royalties that are far, far better than any print-book commission I was ever offered.