Everyone says don't dilute the PR, but what is the approximate numbers?

As for now we have an e-commerce site, with many products. We want our page to be easy slide (as on Facebook scroll down), and it would put like 5000+ links on one page, would this dilute?

As I have seen somewhere that underscore "_" unites the names and Google looks at it like one word with no spaces.

Wouldn't it be bad for long product names?

example.com/2010_chrysler_grand_voyager_2l would be the same as write example.com/2010chryslergrandvoyager2l ?

Just trying to get the best out of everything

In this case, doesn't product-name-111 is all keywords for a page? My product if my product page doesn't consist of 111 it would make a mess for Google.

I can give one example that could messes up:
example.com/cars-1963

And 1963 isn't a year nor it's a model number of a car, it's the ID of a catalog.

Hello,

My company is going to change URLs to example.com/category or example.com/product.

When we will change the URLs to product or category pages somehow we have to check whether the requested page is from category table in DB or from products table (this gives much speed to page load time).

So we have to choose how to make the different product and category pages.
Programmers said that we need to insert id to URL.

So the question is: Which is the better way to place an id to an URL?

example.com/product-name?id=111

example.com/product-name/111

example.com/product_name-111

Or maybe we should use some other punctuation mark to separate id from product name?

p.s. I have read Dynamic URLs vs. static URLs by Google and it still didn't answered which is the best for all of the pages.

Somehow others solve this problem by typing only the names to the URL, but could anyone tell what that technology should be?