I'm a little confused. Can anyone help out?

Hypethetical Situation:
I have a site that receives 2 PR7 links and 2 PR6 links.
Let's say it boosts my PR up to a 6 correct ?
Ok, lets say that after a few BL and PR updates all of my
internal pages (10,000) get their PR up to 5. This should
boost my PR up to a 7 correct?
Now this is where I get confused. After having my PR7
and most of my internal pages a PR5 or PR6, if I loose
one of the PR7 and PR6 links will this PR go away or down?
I mean I would still have 10,000 strong PR5 or PR6 BLs, but
all internally. Would the only way to keep my PR is by getting
it from the outside? or would it be possible to contain PR
from within a site?
I hope you understand at what i'm trying to say here,
because it has me a bit confused as well.
Thanks for the help.
J Fontestad

1. <edit>by fathom, reason: URL removed</edit>

Well, look at it this way. If you lose one or more external links, and that causes your homepage PR to go down, then that loss may very well filter down to your internal pages, so those internal pages now will not be as strong as before. Of course losing one link may or may not affect your PR. It's too difficult to gauge it so precisely, but the general answer is that losing enough external links (whether it's one or 100 of them) could definitely affect the PR of all your pages.

Another question I was wondering about, is that once I get let's say a PR7 homepage
1,000 PR6 and 9,000 PR5,4's & 3's. As the PR ditributes itself throughout my site it
will strengthen the PR of the homepage and of the other main pages on my site? or
can that only be done with external links ? and eventually the internal links themselves
would possibly be able to increase my PR from withing the website without the need of
more external links ?

whooo..... Losing me....... Internal links will increase you entire sites pagerank. As you gain links to your homepage - yes - your internal links will build pr for your internal pages.... then those pages will build pr to any pages that they link to.... If you loss links to your site in will eventually effect all of your pages becuase your homepage pr will go down.... I think I know what your getting at...... The source of the PR, I believe is the deciding factor.... I dont believe that your internal pages could hold enough PR to boost your homepage once and if you where to lose your main inbounds....

Ok,
So providing that I have external links that give my homepage it's initial
PR, then that PR spreads throughout the site and my internal PR elevates
my homepage PR. So, lets say I have 3 websites and I do that triangle linking
(site A's homepage links to site B's, site B's homepage links to Site C's and
Site C's Home Page links back to Site A's, but none of them back link to the
site that is linking to them) if this were the case I'd be able to keep my PR
up without loosing and BLs because all the BLs i'd have would be produced
by myself ?
Can I conclude this theory correct or am I wrong ?

your all three sites are on different -different IP

That will play a factor - If they are all on the same IP address - they may be viewed as a PR minipulation tactic....

That's exactly what it is....

Even if they are on the same IP Range....
EX:

194.58.69.36
194.58.69.37

Range is BOLD

it's only 3 sites and i'm only interlinking them. not for PR manipulation, but because they belong to my network of sites. I beleive that the 3 of them are on the same IP. will i get penalized for this? It's not like it's 25-50 websites... it's just 3.

You have to see PR a vote points. These points come from links. If a link goes, the points goes. The points you get are spreaded to the inner pages of your site according to your site link structure.

If you have 10000 PR points, and lose a link of 2000 points, then you only have 8000 points to spread in your site.
If you don't change your site structure, the pages will go down in PR.

PR is a redundent calculation with a damping factor to stabilize it's value. If home goes down, pages go down, if pages go down they give less points back to home... so it has a big effect at the end.

The initial PR, as you say, is basically how many points you got from the Backlinks and then with your internal structure you funnel these points to the other pages of your site.

Looking at this forum's PR and the nice devshed links at the top of every page makes me think it's not that bad to link your sites together.