Yes. Apps are a step backwards because they are in a much less user-controlled space. App adoption is more correlated with mobile platform adoption as opposed to demand for ad blocking.
Some have ads, but they are definitely not crippled by ads and malware.
Not nearly as much as mobile web.
Not that horrible. I don't use an adblock at work, even if what I'm browsing is limited to the register and HN with the linked pages and it's usable.