If I have to choose, then I would choose according to the quality of their services. But, all factors are important. Also, I would add to your factors:
- The reputation and honesty of the company.
In this case, your best option is search engine marketing and promoting your forum on other forums, blogs, social sites, etc. It will help make your forum visible on the web to a certain limit.
I have been in many forums and I have seen many templates, yet one of the reasons I hang at Webmaster Sun a lot is because of the creativity of the forum template. The template is indeed attractive, friendly and well presented.
Blog commenting is very effective as long as you do it in a natural way and as long as the blogs are related to your subject/content. Also, the quality of the blogs is important and of-course the originality of content.
Most web hosting providers will provide all the features you need to run most types of web sites.
Just make sure you go with a reputable web hosting provider.
Most shared hosting providers would fit your requirements. Once your forum grows you can upgrade to VPS.
From what I know serverpoint has a positive reputation, but I never tried them.
As mentioned by the members, page rank depends on the quantity as well as quality of back links to your web site, while Alexa ranking depends on the amount of traffic your web site receive.
This rating makes no sense at all, as it means there is no service at all. From my experience; PayPal support is good, not the best if compared with others.