I am for adding the company name at the end. If a person is searching for a brand or company, you should have more than a few places where that name or brand is mentioned.

I understand that branding involves much more than this, but due to how the site is set up, I don't see anything wrong with it. You are not extending your title past the character count, not putting your name at the beginning of the title, etc. The page titles are already very short, so I see no harm in it.

With is being so easy to rip off anothers brand name with a domain or URL, I personally agree with using using a company name in the page title, unless your company name is extremely long, and jeopardizes the character count displayed.

Then, there is always this:
http://searchengineland.com/quantifying-brand-bias-search-results-rand-fishkin-moz-189824

I'm sure some will disagree with me, but that's what makes the internet such a great place. Being able to agree to disagree

I honestly see your point, and understand both sides of the dillema.

As long as the replacement ad is highly relevant, and you are already ranking well for the expired ad, you could leave it in place. Ebay is known for doing this, in which an indexed ad is left in place, and you are shown relevant ads like the expired one. This is a risk you are taking. What you don't want to happen is have your users get frustrated by constantly seeing expired ads. I'm betting most people will come to the site by searching, and not by an internal link. You don't want to be known as the company that sells ads, not products.

Morally, no its not right. You should only have an ad for an item that exist, but yes, this method does work, and often.

Schema is designed to let you mark up individual items. For example, when a store has individual product pages, you should have the end page be marked up with data. As far as I know, there is no way to have multiple items maked up at the same time on one page. I'm sure you could code it that way, but I doubt it would be displayed or read correctly.

Here are two resources that may help you:

http://www.schema.org/Product

http://www.schema.org/AggregateOffer