I don't think there is any magic number of keywords ie 7...., your ALT tags should be descriptive enough so that anyone with a screen reader can understand what the image is about. There is no rules about ensuring all your keywords are lower case in your ATL tags but your file names should all try and remain lowercase if possible within your CMS for consistency.
You also don't want to include hyphens between your ATL tag keywords unless they are dynamically generated by your CMS and you have no control.
It may not be prefect SEO tactics but I always ensure my ALT tags and description can be interchanged and remain consistent.
Sure you can find several websites who over optimise and stuff keywords into the ALT tags but in my experience keeping it short to 1-3 keywords has the best chance of showing up in Google.
The title issue can have your designers wanting to stab your eyes out, I've had fights with design agencies in the past because I implemented "title" tags, it's really down to preference but you can use both I would just suggest making them consistent.