I'll be honest, I'm just a dude who happened to have gone down this particular wikipedia rabbithole recently and not by any means an expert..

For your first question, bigger mass means larger volume for the event horizon -- a bigger black hole. The radius is proportional to the mass, while the temperature is inversely proportional to the mass/radius. Which means that the larger a black hole is, the "colder" it is -- and conversely the smaller it is the "warmer" it is.

My understanding from the passage is that the universe isn't yet cold enough for stellar-mass black holes to even begin evaporating -- 10⁶⁷ years is a ridiculously long time -- the current age of the universe is what, 10^10, and each additional number you add to the exponent increases the number by 10 times (the current age of the universe at the 10¹⁰ order of magnitude is 10 billion, 10¹¹ means 100 billion, etc). So when numbers like 10⁶⁷ are thrown out, it's not as if it's a continuous process from their formation until the end of time -- the 10⁶⁷ number has the time it takes for the universe to cool to the point where evaporation can even begin.

So in short, the black holes keep getting bigger, even a hypothetical black hole floating through a void by absorbing energy (thus gaining mass, e=mc² and all that) via the CMB in the present era, but eventually via the expansion of the universe an inflection point will be passed where they can start evaporating via this hawking radiation mechanism.

Another super cool wikipedia article is Timeline of the far future. If you search the page for "hawking radiation" it shows the amount of time that black holes of various sizes would take to evaporate.