You can use Google's keyword suggestion tool , type in fabrication and welding in the keyword list and the website , check the box that says "only show ideas closely related to my search terms" . You should be able to pull a good keyword list using this tool.

In addition to this tool you can also use SEM Rush , type in the client's website and see what keywords they are ranking for that are related to your site. You can also use the keyword analysis tool from SEOMOZ.

Yep, you're on the right track with your thought process. Google will try and give credit to the original source of the content.

I don't think the adding the feed on your site will get you in any trouble as long as you link to the original source of the content. More Info Here

Hi Eric,

more info on the over optimization penalty here.

The length of the content should be based on the actual content itself being presented and the visitor experience. If the information can be provided to the client in 250 words then that's what the length of the page should be.

Here's a link to a good post discussing this topic.