This is looking pretty good. if you are still getting some smoke that is trying to make your life “uncomfortable”, You could cobble together a brush sweep
Good job so far.
What is the current draw on the Vivosun?
I’m not sure on draw for the Vivosun – all I know is it’s not enough to trip the surge protector or cause an error on the Bullet 
So the new setup worked MUCH better than the first attempt. No chaff escaped the garage or the roof vent which was a success. However, there was still some chaff and smoke seepage during the roast itself. I’m exploring your brush sweep idea as well as a couple of others.
I’m wondering if part of the reason there doesn’t seem to be adequate suction from the Vivosun in this configuration is because it’s also drawing from the ductwork leading down to the cooling tray. I was considering installing an adjustable baffle in just below the roaster on the 4" wye and keep it closed during the roast but open during cooling phase. Another option, similar to the brush sweep, is figure out a better “hood” to sit closer to the Bullet exhaust port to catch the loose ends.
At this point its working about 95% to the extent I’m looking for so for now satisfied but will keep thinking on ways to improve it.
When I was falling down this rabbit hole and experimenting, I tried an in-line 4 inch duct fan similar to a Vivosun. The in-line fan was only rated for 50 watts. at 120VAC that is less than 1/2 amps.
It just didn’t have the CFMs (even though it was rated at 285 CFM) and the motor didn’t have the torque that the shop vac did. I doubt that I was really getting 285 CFM after reducing the 4 inch diameter down to 2.5 inches.
I played around with the idea of using a leaf blower to reduce the size and perhaps the noise, but never got around to trying it.
At this point in time for me, the only thing that I find wanting with my current setup is the noise from the Shop vac.
I also thought of making an enclosed cart and have the shop vac inside of the enclosure. That might solve the noise issue.
Like you, I am always looking at ways of improving things. “Kaizen” Japanese continuous improvement
)