Is there anyway to add Do Follow links to another site without spending page juice? What if all outbound links are on the same page? Would this affect rank for the entire site or just the page that the links are on?
Depends mate. Is this a quality, related resource you are linking to? Otherwise, linking to a shitty webresource might affect your whole domain... Not always the case though.
If you did mean "dofollow" link then I would say it's impossible. However, as Google had already fine tuned to handling "Pagerank Sculpting" then even that link is nofollow, your page value is still being divided anyway. Read more here - PageRank sculpting - MattCutts.com
I dont think so. But then, I dont believe that spending link juice will diminish the website. After all, many high ranking sites have tons of outgoing links.
It is a decent web site, good page rank and on their own hook added a link to my site. So, I feel like the least I can do is add one back.