Partial Installation, Including Subdomain

I have three separate WordPress installations up and running now. It’s much more user-friendly than I expected. But I now want to do a custom installation and need some guidance.

I have a domain – https://www.mysite.com – that’s very developed. I THINK I might like to convert it to WordPress some day, but I have a lot of hoops to jump through. So I don’t want to do it yet.

At the same time I DO want to go ahead and add a WordPress blog to the site. I would tentatively install the blog on a subdomain – blog.mysite.com. However, I could probably install it at another location, like https://www.mysite.com/blog.

So here’s my plan:

1. Delete my entire site.
2. Publish WordPress in its place.
3. Set WordPress up on https://www.mysite.com, with a blog channel at blog.mysite.com.
3. Create a WordPress home page.
4. Then republish my entire site.

At this point, my site should be exactly like it was before, except the home page will be a WordPress page.

I think I should be able to do that fairly easily, but I have two questions…

1. How would I set the blog up on a subdomain?
2. I currently have a .htaccess file that allows me to display pages at URL’s like mysite.com/world/france, mysite.com/georgia, etc. When I republish my .htaccess file, is it going to cause problems with WordPress?