Weight and Battery Advice - Newbe

Hi there, thank you for letting me join your forum.. I’m new to quadcopters so please bear with me.
I am currently building a 3D printed quadcopter based on a design I found online with a few tweaks of my own. The quadcopter comprised of the following equipment and I have the following two questions.

Drone frame size - 450
The ESCs are – Hobbyking 30A 3A UBEC with burst to 40Amp – Lipo 2-4s
Motors – Racestar BR4108 600KV 4-6s brushless – 14.8V.
Props – 11 inch x 4.7 inch pitch carbon fibre.
Pixhawk PX4 controller with GPS & Power Module.
Frsky X8R receiver.
3DR Telemetry Transmitter.
ImmersionRC Raceband Transmitter.
Minim OSD Transmitter.
3 Channel Video Switcher.
Fatshark 700TVL Camera.
Gimbal controller
3D printed gimbal setup with 2 2206 Gimbal Motors holding a GoPro Camera.
30cm 12v strip lights in each arm – these are switched off by the controller.
All in all the quadcopter complete with battery is weighing 2.44Kg.

My questions are:

With all this setup it the quadcopter too heavy?

What size batteries should I be using for this to get the best out of it and a decent flight time. I currently have a Nano-Tech 1.8 35-70C 4s battery. This is powering everything but I tried my first test flight today I took the throttle to just over half way and the quad started to lift but being nervous I throttled off, I tried again but then all of a sudden a couple of the props slowed down then they all stopped and the Pixhawk started bleeping, when I checked the battery the voltage was low and one of the cells (cell 1) was almost zero.

I have also had trouble carrying out the ESC calibration, it goes through the calibration as instructed i.e. throttle high then down to zero after tone but the Pixhawk does not recognise it, not sure if this is because of the battery. I have tuned the trims in the Taranis radio so the thr, Ail, ele and rud are between 1000 and 2000.

One last thing, is it best to have the rotors spinning at arming and when at low throttle or have then stopped? They do rotate quite quick.

Any advice you could give would be most appreciated.