I can't believe I missed this topic. I'm not doing well enough at my forum stalking, apparently.
Virtually all of these questions have highly likely answers, except for #7. Also, I will go out a limb on #1, because that question hasn't been directly asked. But, here are my answers for you:
1. No. Metals are the focus for Preservation's power. All burning a metal does is unlock Preservation's power, and thus it grants the particular Allomantic ability corresponding to the metal. Burning should not be taken literally. There are other focuses in the Cosmere, and I asked Brandon once. The Commands in Warbreaker for Awakening, the Aons in Elantris... All of these are immensely magical in nature. I do not believe that "burning" metals would actually produce heat. Remember, these terms are in-world. The first Allomancers probably created the term, and its rather catchy, so it must have stuck, regardless of it being factually accurate.
2. Absolutely. Atium has its Feruchemical power of youth, so Lerasium must have such an ability as well.
3. We do not know that Lerasium-Steel creates a Coinshot for certain. For all we know, creation of Mistings is just another "side effect". I would imagine that whatever Lerasium-Steel does, it will not store precisely the same Feruchemical ability. However, I do not know. There's no basis for that theory, as we do not know Feruchemical powers of any God metal alloy.
4) If someone is Hemalurgically imbued with a Feruchemist's power, could they tap that Feruchemist's metalminds? For instance, Feruchemist A spends his whole life storing senses in Tin, and then is captured by Inquisitors, who use a Tin spike to steal his Feruchemy powers and add them to Inquisitor A. Could Inquisitor A then tap Feruchemist A's tinminds? After hearing Hemalurgy described as "stapling a part of someone else's soul to your own", it sounds like it could be possible. (After glancing through the Mistborn wiki on Wikia, it looks like it would have to be a Brass spike that is used)
4. First of all, thank you referring to Hemalurgy as being "imbued". I need to start a petition for Brandon to use that term permanently. In the MB annotations, Brandon calls such metals "Hemalurgically charged", which I think is confusing it with Feruchemy.
The simple answer to this question is no.
Now, I know this for certain. I had a fellow TWGer ask Brandon at a signing. Basically, just like an Allomancer can't burn another person's Feruchemically charged metals, a Hemalurgist cannot either. In order for that to happen, the spike would actually need to be imbued from yourself, which is more than slightly ridiculous.
5. Others have answered this one really well, but to expound a bit: Inquisitor powers also depended on what skaa Mistings they could find at the time of their creation. That's a major hindrance there.
In terms of Inquisitors "doubling up", does Hemalurgy work like that? If someone takes three Pewter spikes instead of one, does that make them automatically three times stronger than a one-spike Inquistor? Or possibly stronger by a factor of 3 rather than a multiple?
My answer to that would be it depends on the genetic strength of the Allomancers you are spiking. Obviously, spiking someone like one of the Original Allomancers will increase the recipient's abilities much more than a skaa Misting who has noble blood three generations removed.
I also believe that Allomantic strength is a major factor in piercing copperclouds at all. If you were a weak Smoker, such copperclouds would be easier to break. You don't
necessarily need to double up on your Bronze if you already have sufficient Allomantic strength (like the Lord Ruler). I think you just need to break a threshold on Allomantic strength relative to coppercloud you are attempting to pierce.
For Inquisitor's, I'd imagine it is necessary to double up. Inquisitors do eventually die, and in the time of the books, all those immensely strong Allomancers are dead, so an Inquisitor would have less "absolute" Allomantic strength compared with centuries before. But if they double up on bronze, they have more than enough "relative" Allomantic strength to pierce the cloud.
6. Good question! The way I understand it is that those genetic (and spiritual) codes are tiny fragments of Preservation itself. I would guess that there no good way to predict what Misting you will get (or if you will get an Allomancer at all. Tevidian had strong genetics, but I don't think he was an Allomancer). Certainly in noble houses like Venture, there was a lot of diversity in their small amount of Mistings. If Misting abilities were directly hereditary, Straff (Tineye) would have made Zane a Tineye as well, which is not what we see happening.
7. It's very difficult to say. I can't even make a convincing argument there
So, instead, I shall say what my Table of Allomantic Metals says (I knew there was a reason for mounting it above my computer: quick reference!): "In alloy form, it produces various expanded mental and temporal effects." I wonder what that would mean if you alloyed it with a Physical metal... Now
that'd be an interesting question for Brandon.