As a rule of thumb:
If the base form is spelt with a
single final consonant and the final
syllable is stressed, then the final
consonant doubles when endings (-ing,
-ed, -er, -ist etc) are added
Final -l usually always doubles in UK spelling, but generally doesn't in US spelling. There's some variation with "s" (so "busing" or "bussing" are generally both acceptable).
A complication concerns cases where the vowel in the final syllable isn't stressed, but it still carries it's "full" quality (so common candidates are "a" or "i" in a final syllable). So for example, "kidnap" would become "kidnapped". There can be variation in such cases.
Obviously, we're only talking about consonant letters that actually represent consonant sounds (so you wouldn't write "bow" -> "bowwing", for example).
There a couple of misconceptions here. The first is about reduced participial phrases. Generally this means transforming a clause, which has a finite verb, into a phrase with a non-finite verb. Thus
I came to work today while I was wearing my new suit
becomes
I came to work today, wearing my new suit
Secondly, I don't know what grammar is telling you that participial phrases have to modify adjectives. Participial phrases may act as modifiers for any construct that can take a modifier.
Next, I'm not sure what you think a "participial prepositional phrase" is. One example you give is
- This is good result(,) given how other teams performed
but there isn't a preposition in sight.
Participles by themselves don't really carry tense. You seem to think there's a difference in punctuation based on whether there's a present participle (one that ends in -ing, e.g., "coming home") or a present perfect participle (one that combines having with the plain form of the verb, e.g, "having come home"). There isn't.
Most of your examples may be parsed as nominative absolutes. For example,
I came to work today, wearing my new suit.
These aren't really restrictive or non-restrictive because they are independent of the grammar of the main clause (thus the name absolute). The wearing of the new suit applies not just to the subject, verb, or prepositional complement individually. The style manual I use, the Chicago Manual of Style recommends setting off introductory elements like this with a comma. CMOS also recommends setting off following non-restrictive elements with a comma, so I infer the same for following absolutes.
Punctuation is a matter of style, not grammar. So follow the rules in the manual of style that you've chosen or that has been thrust upon you.
Best Answer
Words take modifiers according to their role in a sentence, not according to the root form. Therefore, when a participle functions as an adjective, it takes modifiers (and forms comparatives) like an adjective, not a verb. Thus, you can describe someone as very missed just as you can say they're very interesting or very tired.
EDIT: As StoneyB notes, some people may interpret missed as passive voice instead of an adjective, especially in the construction “He will be missed.” In that case, you're right to prefer an adverb better-suited to verbs. For this context, I would prefer greatly or deeply to very much, as they're less verbose and higher in register: “He will be deeply missed.”