What all is failed? Having a spare bike isn't necessarily a bad idea, especially if you can leave it on a trainer.
Hard to say. Geometrically, what's important is that the bike fits and that you like the handling.
Road bicycle category names aren't very well-defined. For example, "endurance" can refer to a more upright fitting geometry, to a calmer handling geometry, to a softer ride quality, or some combination of those. Road bikes also have a pretty wide range of fit adjustment, so if you're choosing between two bicycles and you select one with a more "upright" fitting geometry, it won't necessarily result in a more upright fit.
I don't consider that obvious. A bicycle frame is as strong as it's built.
In terms of how well they work, the main benefit of disc is that they suffer far less performance degradation in the wet: when braking in hard rain, the brake track gets cleared quicker, and you have more braking while waiting for the brake track to clear.
If rim heat buildup is a concern for you on descents, discs also resolve this. Not to say that they're thermally perfect: sometimes people experience stuff like brake rub after a hard descent due to built-up heat warping the rotor.
If you live in an area with abrasive road gunk, and you ride in wet conditions, discs also ameliorate the issue of brake track wear: braking wears down an easily-replaceable part (the rotor) instead of a more expensive and difficult-to-replace part (the rim). This can be relevant if you're wanting to run super-nice rims on a rain bike.
Discs also eliminate brakes as a limiter of tire clearance. For road, this is a somewhat artificial issue: on rim-brake framesets, the limiting factor to tire clearance is usually the frameset, not the brake calipers. Furthermore, rim brakes exist that are reasonably lightweight, work extremely well, and can fit tires much wider than the traditional road widths; they just haven't been fashionable on performance road bikes.
That said, in practice, the expansion in tire clearance on road bikes is fairly well-correlated with adoption of disc brakes.
The benefit to rim brakes is that the overall bike tends to weigh a bit less: disc brake systems tend to be slightly heavier, and the framesets also tend to weight more because they need to resist high twisting forces from the brake calipers.
If you're buying new, this comparison is probably irrelevant, because the industry committed to discs years ago. There are almost no large-brand production models left using rim brakes, outside of some entry-level options.
Depends on where you are and what sort of riding you're doing.
For example, if your regional gravel consists entirely of velodrome-smooth groomed hardpack like this...
...then you might genuinely not have much use for tires >28mm even if you're doing lots of gravel. Meanwhile, if your gravel roads are all pretty rough and frequently have long stretches of chunky stuff...
...then it might not be worth trying to accommodate gravel riding at all unless you choose something with clearance for tires that are waaaaay wider than the traditional road widths. (Not that this is a bad option, as it's often possible to achieve a high degree of versatility while giving up very little.)
Definitely don't get a slow bike if you want a fast bike, but I'm never quite sure what the frame of reference is for that judgement. Bikes marketed as "endurance" bikes sometimes get ridden to wins in WorldTour races. If your riding is more suited to such a bike, it's not obvious why it would be slow. On the other hand, it's also not obvious why you think that your riding is suited to such a bike.
There's not really much je ne sais quoi to bicycle speed. Things that slow a bicycle down slow it down. The label that gets applied to a bicycle doesn't do a whole lot.
Here's my 1970s Fuji America, originally sold as a "touring" bike but nowadays usually described as a "sports tourer."
Here's my Emonda, which Trek describes as a light, responsive performance road bike:
As pictured, my performance on those two bikes is nearly identical when riding solo on flat ground; if a quick eyeballing of recent ride data is anything to go by, the Fuji might actually have a narrow edge in this regard right now. The Emonda does tend to do a hair better uphill, albeit not any more than would be expected given that it weighs seven pounds less and that the integrated shifters allow easy shifting out of the saddle under power. If I tossed some good aero wheels on the Emonda it would probably gain an unambiguous advantage, although the same argument could be applied to the alleged "touring" bike. While the two bikes do feel quite a bit different from each other, I would not hesitate to apply a description of "lively" to either one.
This isn't to say that the Emonda sucks* or that you should go buy a steel bike from the 1970s**, but rather, that people often put a lot more stock into the marketing labels and stories than I think is warranted. When a salesperson decides to call something a "racing bike", this doesn't magically slap a speed bonus on it or whatever.
If you like that Orbea and it will work for you, get it! But don't get it out of some kind of bicycle marketing categorization FOMO.
*It doesn't.
**Unless a steel bike from the 1970s is what you want, in which case, you should buy one.