Squarespace to WordPress migration issues

I recently imported my Squarespace blog into WP using the WP importer. Squarespace generated an xml file of my content.

After running the importer tool, I have noticed a number of issues that I can’t seem to resolve. I am a relative newbie – so I apologize if my terminology is faulty!

1. All of my post slugs (>1500 of them) are incorrect. They have a 7-digit number (date) added to the front of them:

this-is-the-desired-slug has become 2013524this-is-the-desired-slug

I have searched high and low for the easiest way to correct this. I was hoping that there would be a plugin that would regenerate all slugs using the Post Title, but can’t seem to find one! ??

I’d like to retain the old site structure so that when I point my domain from the old host to the new one, all the links work.

2. Most of my images were not uploaded to the new WP host – they are still being linked to the Squarespace server. Any suggestions on how best to correct this problem? Obviously I will need to get all my images off the old server. How would I update the post image links to point to the new local media location?

3. Bearing in mind I don’t have access to the old database (Squarespace is a closed platform) – does anyone have any tips on how best to switch hosts so that I don’t lose SEO info, page rankings etc? I will point my domain name to the new WP installation folder on my new host. Should I keep the old site up?

4. Will my Google Analytics UA remain the same? And my Akismet keys? Or are they linked to the old IP?

Once again – please forgive my incorrect use (or misunderstanding) of the terms/concepts involved.

Thanks.