Google develops Android and markets it, and I would assume that they could be sued for developing an infringing product. Google most certainly makes money, and a lot of it, from Android.
But Google makes no phones on its own, unlike HTC and Samsung, so Apple goes after those companies to keep the devices from being imported into the US. And Apple can fight Android in a legal proxy war rather than directly suing Google.
Could you explain how you are most certain of this? I don't believe they make any money from Android. If you mean they make a lot of money on ads from customers accessing their services via a mobile device -- then fair enough but that's not "from Android" any more than they make tons of money "from the iPhone".
Would love a source on this... AFAIK Google never publicly said Android Trademark and Google Apps were not free (apart from the obligation to pass the CTS test suite)
They may not be suing Samsung over this particular patent, but that could easily change.
No, worst case is that Apple doesn't see a reason to grant a license and effectively blocks the sale of HTC Android devices until they remove whatever it is that they're "violating" here (and what that is I have no idea).
If you were to apply the "oh $CORP got sued and lost a patent lawsuit - I might want to dump $CORP product" uniformly - you will be left with no products to buy in the mobile space at least!
Why is HTC being sued and not Android - Because HTC is an corporate entity that makes money off Android - Android isn't a corporate entity on its own - who would they sue if they wanted to sue Android?