First Build - Featherweight Bar Spinner

[Dr. Crane]

Hi everyone - I am totally new to anything engineering-related but after many years of watching and admiring the robots on Robot Wars/Battlebots I've decided to get involved!

I have spent probably a year perusing this forum and looking through the various build diaries etc. and thanks to the endless wisdom and generosity of this community I think I've picked up quite a few pointers.

My main obstacle (besides my lack of knowledge) is that I have pretty much zero access to a workshop and no space in which to build my own. To this end, I am hoping to spend lots of time on the CAD and then get a CNC machinist to machine most of the parts. I'll then be bolting it all together like a jigsaw and doing the soldering etc.

Moving on to my concept - it's a featherweight spinner with a rather unoriginal design but my main goal with this first build is robustness and reliability over innovation.

Frame: 1/2 inch 6082 aluminium
Drive: 2x Nidec DMN37KA motors (3600rpm) - geared down about 2-3:1 depending on the size of the wheels.
ESCs: Drive - 2x tz85as which I've already reprogrammed (that was quite an adventure!) Weapon - not sure yet
Weapon: 2kg Hardox Bar Motor - 270KV Brushless Outrunner from HK Geared about 2:1 Shaft - 20mm titanium
Batteries: Drive - 5S 30C 4000mah LiPo Weapon - another 5-6S LiPo
Radio: Turnigy 9x
Wheels: - ~120mm Nylon with rubber treads bolted directly to the pulleys, 4 Ball Transfer Units at the front
Belts: 9mm Timing belts for the drive with aluminium pulleys, round belt for the weapon with aluminium pulleys
Armour: Depends on the final weight

I do have a few questions and would be grateful for any help!

1. When calculating the final gearing, I was wondering if there are any good ways to estimate the rpm a motor will put out under load. For example the 270KV outrunner - I have no idea how well that would spin a 2kg bar.
2. I've been looking at using a round belt for the weapon drive - does anyone have any experience with these?
3. Following from Q2 I was thinking about possibly using a chain but I'm not sure how to create a clutch (I found one in the RioBotz book which uses a belleville washer but I don't really understand how it works).
4. Does anyone think the ball transfer units at the front are a bad idea?
5. Finally, does anyone have any ideas how I could simplify this design? I got a quote from a CNC machinist nearby and I'm probably looking at £500 at least to get the bulkkheads and 'V' shape frame cut (one V is made of two parts - £60 + VAT per part).

Thanks for reading!