Hello. Most probably weak point in your setup is ESP or wiring. @vshymanskyy was able to build copter via Blynk with low latency.
No.
It would’ve been nice to see how the widgets send their data (how often, how large the data is)
This info is open. Briefly - 5 bytes header + body. Body is usually 8-12 bytes. You may think that this is a lot. But considering TCP/IP packet header itself (40 bytes) this not much. So your packet is 43 bytes. Blynk packet is ~55 bytes. So in terms of latency this is almost the same. Also for joystick and slider we cut 2/3 of events, cause our tests show that most of hardware cannot handle such load. And ESP if one of the weakest chip here.
Yes, we even have internal prototype for that. See our roadmap here. You may vote for direct connect to make it happen faster 
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It repeats the functionality of slider.