I would assume that there is no set number of links that you could exceed. Some sites have TONS AND TONS of out going links. If you are interested in the benefits of linking out for SEO, then I would imagine 3-7 wouldnt be a bad number
Do you mean blog roll links you can give in your blog. I think up to 10 blogroll links are okay, but they should be of same or relevant niche as yours. i have given about 10 links myself and till now i found no problem.
Better little only bcz more Outbound links google will consider it as link selling then will be in trouble. But like directory, forums, blog site there is no limit u can see millions on it and there is no problem for them
I've read that less than 10 also...try to get links in pages with the less outbound links possible, this way the PR "juice" is shared between less sites
There is no safe amount, having alot of out going links wont hurt you, but the more links you have going out from a page the less "link juice" those links will have. If those are links to internal pages on your site, or links to other sites you own, you want them to get as much benefit from that pages page rank as possible. for example if you have a page rank of 2 and 2 out going links on that page, the value of the page rank that is passed onto those outgoing links will be divided between the two. If you add another outgoing link the pr is divided among those three outgoing links. Each outgoing link dilutes the link juice of outgoing links. Also a whole lot of links with little relevent content could be seen as a link farm, and you could be penalized by google.