Don't sound right to me. A 2S Lipo fully charged is 8.4V. How can pumping 5V into it get it to 8.4V? Unless the batteries have some internal circuitry to up the voltage.
Keep in mind that any batteries simply connected in parallel (charger off) will naturally self equalize.
Let's say one battery reads 4.1V and the other is 3.9V, if you checked them a minute later both would now be at 4V. That said it's not recommended to parallel batteries with a wide...
I doubt it. I'd stick with a Micro SD Class 10 And above or UHS-1 Micro SD Card, max 32GB.
That's from the specs for the Eachine EX4 which appears to be the same quad.
Wrong one, older tech. Get the X with this smaller, lighter, newer RX.
https://www.banggood.com/Flysky-FS-i6X-2_4GHz-10CH-AFHDS-2A-RC-Transmitter-With-X6B-i-BUS-Receiver-p-1090406.html?rmmds=search&ID=42482530817&cur_warehouse=USA
Are you recording to an sd card inserted in the drone itself?
These antenna kits are cheap with good reviews.
https://www.banggood.com/Hubsan-H501S-H107DH502S-Enhanced-FPV-Distance-5_8Ghz-14dBi-Panel-Antenna-2_4GHz-3dBi-Antenna-p-1053146.html?rmmds=search&cur_warehouse=CN
It should do 4K video, if that's the version you buy. In reviews the 1080p looks quite nice. FWIW in pro photography for photos. they talk in megapixels.