I’m still very new to this so please take everything I say with a grain of salt, and if someone disagrees probably listen to them over me. (Edited as I slowly expanded my answer).
Absolutely right.
To try get a more authoritative answer I checked my copy of A Dictionary Of Basic Japanese Grammar which says that root entry is けれども with A けれども B meaning although A, B.
It then goes on to say that the informal versions of けれども from least to most formal are けど ＜ けども ＜ けれど.
I think this is correct, we can view んだけど as a contraction of のだけど, with the の being explanatory/reason and だ being the copula.
Many dictionaries (e.g. Jisho, and my grammar dict) list だけど as an entry, I think it is copula + けど but I’m not 100% confident.
と has lots of different meanings, here I think と means “with”
For example 友達とレストランに行きました means I went to a/the restaurant with my friend(s).
で also has lots of different meanings, one of them is for “expressing weak casual relations” (this is the phrasing used in A Dictionary Of Basic Japanese Grammar), the English equivalents for this usage of で are “because of; due to; because; and”.
So I think a very rough translation for this sentence fragment might be (page 19)
“Due to urgent business with (all my) familiars …”
or
“On urgent business with (all my) familiars …”
Here I think って is actually a tricksy は like particle (see below for more on this fragment).
This I am absolutely not confident on, so best we have someone else weigh in at some point, and for now take everything I say with handfuls of salt.
I think if we said Xがない that would be a phrase (noun-が-verb) which would mean “there is no X”
But here we are using it in front of a noun (to modify that noun) so XのないY is “a Y without an X” or “a X-less Y” - with this whole unit itself still being a noun (or noun-phrase)
The closest English equivalent of のない is probably “-less”
If we look at this whole sentence fragment 舵のない船って…
In English this gives us
A rudder-less ship は …
or
A helm-less ship は …
I don’t think this is related to ともいい, instead I think this で is more like “and” (same で meaning as above I think).
If you combine this with my comments about on のない and って you might be able to get the sentence working.
Yeah I think so, this character’s speech in particular is quite quirky.
Not sure, I also found that a bit confusing.
If I was forced to guess
If earlier 舵 meant helm, then a helm-less ship wouldn’t be able to be steered, but… magic so not sure that checks out.
I think this is the only part of your question I didn’t touch on, and I don’t have a confident answer sorry. Hopefully someone else can chime in.
I did find a Jisho entry for いろいろあって, but I’m not confident on it. In my initial reading I didn’t pay much attention to this あって, but it is a great question that I’d love to know the answer to.