I'm a sax and clarinet player, so I'm not sure how well my advice will apply to a double-reed instrument. First a generalization: it looks like you're heavily involved in music, so I would seek as much advice from as many woodwind players as you can talk to and practice with.
The tongue is a big muscle, so the trick to rapid tonguing is to move as little of it as necessary -- of course more easily said than done. Some teachers insist that you use just the very tip of the tongue, but many fine players claim to have better results with the part of the tongue just behind the tip.
Often the difficulty with articulation isn't necessarily how rapidly you can tongue or move your fingers, but with
coordinating the two. I would work on stacatto scales and arpeggios (where your fingers are sort of on auto-pilot) but with strict attention to getting your tongue and fingers working together and rhythmically smooth. Then slowly build up speed.
As for the "nasal" sound, I have no advice whatever, since I think it's specific to your instrument.
As you may know, vibrato on single-reed instruments, such as I play, is done mainly with the jaw & embouchure, while vibrato on flute and oboe is done mainly with the diaphragm and breathing. So I really can't help you there, either, but I suspect that nice, smooth vibrato takes a lot of time to develop, as it did for me on the saxophone.
Wish I could give a more helpful answer -- oboists are not that common around here.

Keep practicing and good luck!