Are you a linguist? You have answered these questions with a level of precision that is commendable.
I don't study it formally, or do it professionally, though it is an obsessive hobby
I'll give more detail if you want anything specific. I just didn't want to be too harsh on anybody reading it who didn't want a load of linguistics in there...

That's good. The glottal stops don't sound very nice.
Having said that, in the cluster /tn/, I usually get a coarticulated glottal stop with the /t/. I also get this with word final /t/ when putting particular emphasis on a word.
In fast speech, I sometimes seem to voice consonants where someone with glottal stops would use one. I haven't quite figured the pattern though. In <I don't know that I am>, I have a [d] at the end of <that>.

Oh, that's normal for UK English. The phenomenon I was talking about was Boston English, which puts an -r on the end of words which end in -a, yet drops postvocalic r's in words which officially end in r. Therefore, Korea receives an r ending (Korea-r) and career loses the -r (caree-ah) and the first sounds like the accepted American pronunciation of the second, and vice-versa.
Interesting...I hadn't heard about that before. I don't do that, though I do have r-sandhi (the most prolific of the two main types in the UK). This has spread beyond words that originally has /r/. So, for example <Korea and Japan>, I insert an r between <Korea> and <and>.

I had a friend who spoke Swiss German...it was nearly unintelligible for me.
I've never heard Swiss German, though my relatives don't find it easy either I've read about it having some forms midway through the High German sound shift, for example [xk] in <machen>, but I don't know more than that...


~netweaver~