QuickBase as CRM

The short answer is yes, Quickbase can certainly be used as a CRM, however Quickbase is not built like your classical CRM with the built in features tying it to your email or phone so some things will need to be bolted on/integrated if you truly go that route. 

Of your bullet points - 

1. This is probably feasible - you can use native notifications and set up campaigns and leverage Pipelines as needed, however this is not a marketing platform so if you're looking for metrics like click through rates, read versus unread reports this will fall short
2. I'm not familiar with Aircall, it wouldn't be an out of the box integration but if Aircall has a public API for you to use, Quickbase can be integrated with anything
3. You could do this with an Everyone on the Internet role set where you publicly expose a calendar/form and allow external users to add but then nothing else
4. This gets tricky. Quickbase is not a VOIP system, and never will be. I've seen integrations with VOIP systems like Ring Central get really hairy as well. Tracking points of contact/interactions can similarly be tricky if you consider that you might want to track emails, phone calls, left voicemails etc. Users could do that manually but if you're making 30 calls a day and sending 50 emails, thats not manageable to integrate/try and track in an easy manner within Quickbase. Of your list this is probably the weakest point in functionality
5. This one is easy - similar to (3) you can make on internet role for users to fill out - Quickbase would be great for this
6. This is also easy - you can set up the reporting and tracking for this no issue. 

As you evaluate - I might also suggest/consider you looking into free CRMs as well that can integrate easily with Quickbase. For example Hubspot has a lower tier where you can do contact and touchpoint tracking, but some of the reporting is pretty weak. You could marry Quickbase to it with an easy integration that pulls over the relevant info for things like your surveys and reporting, but your sales team primarily just uses Hubspot for its core CRM functionality.