Update: The Chicago Manual of Style (16e, §6.2) explicitly recommends against italicization "with" the adjacent text:
All punctuation marks should appear in the same font—roman or
italic—as the main or surrounding text, except for punctuation that
belongs to a title in a different font (usually italics).
It also offers the following example sentence "For light amusement he turns to the Principia Mathematica!" with the final exclamation mark being not italicized.
In brief: Publishers wouldn't emphasize the punctuation in your two examples. In other cases the answer is usually semantically "no" (if you're looking for a linguistically backed-up answer), but some people make other recommendations based on consistency of visually proximate elements. Note also that many areas of typesetting have no widely agreed-upon conventions.
I was also going to quote the same passage from Bringhurst as user @cgnieder just did, but with a strong caveat:
Styleguides are linguistically prescriptive, not descriptive. Prescription is full of opinion and very often based on personal history and tradition than on either descriptive reality or what makes the most sense.
Bringhurst is a typographer with an established track record, good taste, and generally a critical mind, unafraid to question the practice of others.
With this in mind, do consider Bringhurst's recommendations. I however perceive language in strongly structural terms. Punctuation is intended to aid in parsing; that is in fact the only purpose of punctuation, unless you use it artistically (eg, in poems) or for special effect (eg, in advertisements). Whenever I read language, I parse it, and whenever punctuation is discordant with the semantic structure or underlying linguistic constituency, I have to stop and I am bothered. Semantically, using boldface is an emphasis of an expression, but a comma is almost never part of the emphasized expression (unless the expression is an entire sentence or the comma is somewhere in the middle). So semantically, it "shouldn't" be boldfaced or italicized, though Bringhurst's argument is clearly a visual one (based on what's visually proximate). I very much respect his point of view, but for someone like me who pays a lot of attention to semantic structure, I must state that my preferences differ, for a good reason.
(A note on the side: Semantic structure is also the reason why so many people disagree with the American prescription to always place a comma and period before a closing quotation mark.)
As for the examples in the original question: italicization here emphasizes only the "this" and the "nothing", and the following punctuation mark is not part of the emphasized material. The sentence structure is something like [[This [is EMPHASIS(nothing)]].]!
, with the period being eaten up by the exclamation mark. I guarantee you that there is nary a publisher who will italicize the exclamation mark (or the question mark) in such a context. The string "nothing!" does not form a linguistic constituent, so if you emphasize both the "nothing" (deepest in the sentence) and the "!" (most outside in the sentence), either (a) you need to emphasize the entire sentence to cover both, or (b) you emphasize them separately. But your question was: "If I emphasize [only] 'nothing', does emphasis of the punctuation mark automatically go with that?"
So my argument is really about semantic constituency: when looking at the tree structure, "function application" (by for example the "quote me" function or the "emphasize me" function) usually applies only to constituents (that is, subtrees), with exceptions being rare.
Bringhurst's italicization example breaks that rule (or you could italicize the "islands of" and the "and" as well, treating the emphasized material as one big constituent and not as an enumeration of separately emphasized ones). But his breaking of the rule I'm stating is not the end of the world, esp if you're more of a visual person and don't do structural parsing as much.
I stated this as a "rule", but is is really one? First, I think that as a descriptive generalization it is correct. (Note that the rule applies to the underlying semantic structure: certain expressions with discontinuous surface constituents, such as German verbs whose separable parts are somewhere else in the sentence, still form an underlying constituent.) Second, it follows from linguistic/syntactic considerations: function application only ever applies to things that you can structurally group together. So it makes sense to be wanting to apply this rule to the scenario here as well.
Back to your question: There are for sure special contexts (fonts, visual layouts, etc) that can make italicization an okay choice there. Or you could decide to independently emphasize sentence-final punctuation in a sentence (for some special reasons).
Btw, note that Bringhurst's examples do not actually cover the cases presented in your question.
Generally speaking: Styleguides and typesetting manuals differ widely in their prescriptions. Some of this is unregulated area. Beware especially of dogmatic adherents to one philosophy (eg, beware of people rabidly defending American practice for punctuation mark placement without ever having seen other linguistic areas do things differently, beware of people treating Chicago as dogma even though they've never read even a fraction of it, and beware of people who cite Knuth's decisions as ultimate truth – I'm not finger-pointing and I don't have anyone in particular in mind, but just be aware that his practice and terminology are not universal dogma and thus please be suspicious of guides and manuals that treat it as such). Especially in areas where there is no obvious consensus and where sources are scarce, you are free to make your own decisions.
PS: I wish SE'd add an italic correction ... this makes the question's option #2 look ridiculous, even though it shouldn't. If all books were printed like SE posts, italicizing the "?" and "!" here would become a necessity to prevent horizontal glyph overlap.