Each country must have a separate (autonomous) homepage, navigation menu and content. It looks like I can do this by creating separate magazines for each country. Can you confirm this?
You can use 1 Joomla! instalation (recommended) or 1 for each country. With both options you can set a magazine front page per country.
I don’t want articles to be published in separate issues. Can a magazine be published in one ongoing “issue”?
Yes, no problem.
Assuming I don't have separate issues, could each magazine (country) have separate sections, eg business, lifestyle, shopping, etc? And if so, can they be featured on the main magazine homepage?
Yes and No.

You can´t have browseables sections (business, shopping, etc) but you can use the header articles in order to show your articles by sections.
Ex.
Article 1 - Header "Business"
Article 2
Article 3
Article 4
Article 5 - Header "Shopping"
Article 6
Article 7
Article 8 - Header "Restaurants"
.
.
.
Etc.
Can you tell me about incorporating images in articles?
In your articles you can add all the images that you need. When you include the article into your issue, you can add just one image per issue.
What will the URL for each magazine homepage look like?
If you use 1 Joomla! instalation for each country you will have yourdomain.com/country_x/. If you use a single Joomla! installation you will have yourdomain.com/magazine_x/ (using a SEF extension. ex. SEF Advance) and each country will have its own magazine.
Can you describe how/where articles would be archived and accessed (linked-to and organized)?
I don´t understand this point. Can you explain in detail?
Can an IM Author Profile contain a link pointing to their Community Builder Profile?
At this point we don´t have our "Author Profile" integrated to CB. Anyway, you can add this link manually.
Do you know if Jom Comment works with IM articles?
Yes, it does.
Could latest forum posts (Fireboard) be integrated in a magazine's homepage?
You can use the latest forum post module in any iJoomla Magazine section.
Do other plugins adding functionality to Joomla pages (eg Clicksafe AdSense Module, ParaInvite, Social Bookmarking) work with IM pages?
Yes, they do.
Thank you. I will report this.
Best regards,