1- Today it really depends on the specific domains you're looking at. The one super important factor most people here have forgotten is cost/price. Today in Oct 2016 .com is still the preferred .. but if acquiring the .com is going to cost you $40,000 versus a standard gTLD registration at $10-$40 then the gTLD option might be the better one. Conversely, if buying the .com is only going to set you back up to a couple hundred dollars (or especially just a $10 hand-registration) while the gTDL you're looking at is a premium, then .com is a the brainer choice. If the medium term price points (including renewals) are about the same then .com is still the way to go.
That being said .. I think in the majority of cases today in 2016, the more expensive option for something decent will actually be in the acquisition of a good .com, so I wouldn't automatically say go with .com .. it really depends on the specifics.
2- No (and yes). As much as old school domainers with 20,000 .com's don't want it to be true, there will be a point where gTDL's do reach a certain critical mass in the public eye. 3 years ago I was one of the very few saying driverless cars were 7-8 years away, and everyone said I was crazy .. yet here we are now .. with driverless cars just a few years out. I think the rise of gTLD's will be the exact same thing .. with good .com taken, people will turn to much better gTDL's .. it won't be everyone, but it doesn't need to be. Just the other week I saw a medium sized business flash a 3 L .co at the end of their TV ad. As this happens more and more we will see a snowball effect pushing towards better gTLD awareness. When that happens new businesses will turn to better shorter gTLD's instead of the only available .com's.
At that point I think it will STILL be the same value judgement I mentioned above for your first question, but the decision based on price point where you'd go for .com before gTLD will be shifted much further towards the better (left of dot) gTDL (not completely though .. just closer than it is now .. .com will be strong for many many many years .. which ironically is why it could be too expensive an option).
3- Theoretically everything left of the dot is supposed to be the same, so hippo.com, hippo.org, hippo.co and hippo.pet are all supposed to be the same in terms of SEO. Some say age might be a factor so getting and aged hippo.com MIGHT beat out on a new hippo.pet. So unless you have access to Goggle's search algorithms, there is no real way to know for sure or how much a difference it makes.
IMPORTANT: .com is
NOT king ...
CONTENT IS KING! Never forget that. At the end of the day your actual domain is an ever diminishing factor in organic search. Although it is a big factor if outside marketing/branding is important to the business. Remember the so called "radio test" .. whatever the domain, your goal is that if someone hears the domain on a radio ad, they should remember it the next day (if you're looking for more than just search engine traffic).
What I'm not sure of however if left to right spanning the dot is the same. Meaning that nicecar.com and nicecar.car are "supposed" to be the same, but it is conceivable that nice.car is just equal to nice.com (although I doubt it). I'm also pretty sure that in Goggle's fight to keep searches relevant, it's only a matter of time before they do start using right of dot relevance as a factor (if they haven't already).
WARNING: While I do think gTDL's will become more and more relevant sooner than most might think .. I do NOT thikn all gTLD's are created equal. For your specific example, there is a problem in that I think there's actually going to be at least 4 gTLD's for the auto industry: .car .cars .auto and .autos .. mind you one could argue the same problem with nicecar.com nicecars.com niceauto.com and niceautos.com .. but for some reason I think split TLD's will be more confusing (don't ask me why .. it's more a gut feeling). And there are other factors in what I feel is a very wide range of value of the various gTLD's that would likely take a book to explain.
So to sum up .. unfortunately at the end of the day I don't think anyone can truly tell you which is better for for you ... as it totally depends on your budget and the scope of your intended business. It also depends on Google's secret and constantly evolving search algorithms .. which nobody really knows about for sure (or at least nobody who is actually going to tell you .. lol).
But as I've said before .. all this is just this relatively new domainer's 0.00003 bitcoins worth .. so take it with a grain of .SALT!
