In fairness to those posters, they are actually correctly identifying the problem which does actually answer the question that you asked originally.
How deeply google crawls your site depends on PR.
So, logic dictates that the only way you can get those pages crawled is to link to them from the higher PR pages of your site. You say you have a PR5 and a few PR3 inbound links. If you have a decent linking structure you will have some PR4 pages in there.
Is there anyway you can link from those, rather than the PR1 page you are trying to link from?
I would guess your site map is (or at least should be) a PR4. That would do the trick.
On one of our lower PR sites, we get all the deep pages crawled by just shoving them in the site map.