English did not originate from Dutch.. Modern English originated from Anglo-Saxon which is a mixture of a group of Germanic dialects spoken in areas around the North Sea. Dutch didn't even exist back then. Dutch is a cousin of English at best considering their shared roots in Ingvaeonic languages. English has also had significant influence from Norman French after William the Conqueror's invasion of England.
Dutch is actually not an Ingvaeonic language, but an Istvaeonic one. Both still West Germanic, but Ingvaeonic language (North Sea Germanic) is the northernmost branch of West Germanic, touching the ‹Westernmost› North Germanic language, Danish (westernmost is in quotes because Danish is actually as East Nordic language, the literal westernmost Nordic language being either Icelandic or Greenlandic Norse). A lot of the similarities between Dutch and English are through convergence, rather than direct relation. If you look at the roots of the two, Istvaeonic is much more similar to Irminonic (e.g. German), whereas Ingvaeonic is very similar to Old Norse in background (compare Old English and Old Norse, which used roughly the same alphabet and for some time retained a large amount of mutual intelligibility).
It's not. It's monophthongal and it's an open back vowel. It might sound like doubt to you because doubt is diphthongal and the range of sound movement from the initial open front vowel to the closed near-back vowel sort of 'glides' past the open back position. Listen more carefully.