They are not exactly the same. You'd be understood either way, but an English person might wince at your style: silently, if they are a gentleman or gentlewoman :-)
Use "between" when your immediate phrase mentions the adjacent objects, and "in between" otherwise. For example, "The Science Museum is between South Kensington station and the Royal Albert Hall." but "Follow signs from South Kensington to the Royal Albert Hall and you'll pass the Science Museum in between."
In effect, "between" refers to the relationship between adjacent objects whereas "in between" refers to the position in between them (and exchanging them in this sentence would be very wrong).
Think of "between" as a preposition, but "in between" as more like an indefinite pronoun of position.
It sounds a little weird to translate 'He lives among us' with 'Hij woont tussen ons'. 'Tussen' signifies placement of something between other things and there's not much room for a more figurative translation (maybe a tiny little bit ;-).
This sentence is 'Hij woont tussen ons in'. That pretty much makes it impossible to translate figuratively. In English you could stress that difference by translating 'he lives in between us'.
'He lives among us' would be 'hij woont onder ons' in Dutch (figurative menaning of 'onder'!).
This is a really interesting question I've never thought of before, thanks for bringing it up. I have a hypothesis someone can support or refute or build off of... I think for certain words like "tussenin" (inbetween), "omheen" (all-around), etc. that are made up of two words and describe the position of something, the two parts of the word split to encompass the location they are describing, thus "inbetween us" becomes "tussen ons in" and "all around me" becomes "om me heen". The exception I can think of is when you involve "er", cos you say "Ik ga er naartoe" (I go to it) but "Ik ga naar het einde toe" (I go to the end).
Aha, check this out! I can't find much info on circumpositions in general, but these seem to be the class of word we're looking for, and the examples given in the individual pages seem to support my hypothesis.
I hear 'tussen ons' clearly by the new female voice on this page, but 'tussons' in the male voice on the exercise page, except when I play it slowly. It is difficult to understand when parts of the word are partially swallowed, but I take your point El2thek that this is normal, and so I think it's valuable that we hear it as it is spoken, even if it isn't as clear.
'Inwonen' is a separable verb, but it means something different! It means that you are living in someone else's house with that person (or those persons). 'Inwonen' also uses the preposition 'bij'.
'De student woont in bij zijn tante' meaning 'the student lives with his aunt/at his aunts place'.
'De oude man woont in bij zijn dochter' meaning 'the old man lives with his daughter/at his daughter's place'.