Lot's of good advice here, so I'll just weigh in with my two cents...
Instead of redirecting all your files to /index.php, why not rewrite those in .htaccess to redirect back to the original (without the /index.php)
This has the dual effect of preserving your link equity to those original urls, and there's a slight correlation between shorter URLs and higher rankings (in part possibly because shorter URLs have a higher click-thru rate)
Regardless, I suspect a perfect storm of factors contributed to your rankings, as you stated yourself:
1. Site was down when on old US host for a minimum of 3 hours one day and perhaps longer
2. Changed from US host to host based in Spain
3. Analytics stopped recording data for 3 days and site was down briefly after the change of host
4. All original URLs now have /index.php at the end
I purposely left out a Google Algorithm change, because of Occam's Razor - the simplest explanation is usually correct, and an algorythm change would be too much coincidence.
As Robert said, make sure you're targeting the right country in Google Webmaster. Other than that, I would try very hard to return all URLs, hosting and settings back to their original state before all these changes.