Welcome to the Q&A Forum

You can modify the title how often you whant but be carefull that it is relevant to the content of the page and the most important keywords in title are in your content. You can read the begginer guide from seomoz on page optimisation, or google webmaster help

Currently images are named changing-cassette-1.jpg + text description, then another image with number 2.jpg and description to that and so on. It will be quite hard to name it accordingly to content. File name could be then pretty long in order to make it making any sense.

I think a key thing to remember is that you should optimize for users and then search engines, not engines and then users. Using the same 4 keywords in every title is not going to add much benefit to ranking well in Google and it is going to look really funny to users. Also to remember is that that title is what will (hopefully) appear in search results pages. You want to write something that users will click on. For example, take a look at SEOmoz's homepage "SEO software. Simplified. | SEOmoz" That covers all the bases, includes the main keyword, but in a natural sort of way. I would definitely use a " | company name" at the end of the title, but I would rethink your use of keywords.

No point in irrelevant linking. There's no harm in going back and adding links once you have relevant content to link to, sometimes you even change where links are pointing, but I wouldn't aim to have X amount of links in each article. For my own sites the more powerful the page the more likely I am to put extra links in but as a rule I try not to have more than 3 links in the body of an article. But, simply linking when it seems useful is a good rule of thumb.