I wouldn't use the exact same META keywords on every page; Google Webmaster Tools will complain about it. If you're talking about the 'content' on the site, well then sure... if that's what terms you want the search engines to find your site.
Google not consider meta keyword tag, so i don't think that there is any problem using same keyword tag, but Title and description should be different for every page. Use best keywords in Title tag.
If google does not consider meta keywprds.... does that make any sense that i still spend a lot of time considering meta keywords???
Mixing it up a bit is the best...Use some of your related keywords and you will get better results.. Best Wishes
Yes, you should have different Title, Keyword and Descriptions on each page or Google Webmasters will complain about it and may even cost you some SERPs.
No!! How will google know which page to rank for the keyphrase if they're all the same? Lets say your site is about dogs. Have the following variations Homepage - Dog Advice, Tips, Tricks & Training Dog Training - German Shepherd Training - Collie Training Dog Food - Dry Dog Food - Complete Dog Food - Working Dogs Food etc. etc.