There's two main ways of doing this:
1 - Jap diff born with discs. Personally I think these are expensive, with average brakes and apparently a very average handbrake. I don't have much experience here regarding the rest of your points.
2 - T series diff from something originally drum braked. T18 is a straight fit, others can be adapted relatively easily. Then add drum brakes from a live axle ST131 or similar Corona. Usually cheap, with a very good handbrake.
- You can use the standard master. I've used an R32 non-ABS master (3 port).
- Using the R32with the proportioning valve completely removed (lines running directly to the master) the bias seems good.
- Take the rear section of the handbrake cables from the Corona too (they're attached to the brakes, so it's hard not to take them). You can use a shorter front handbrake cable section so lengths suit. St162 or SV11 maybe, Parrot wrote a good description of the different options on Toymods about 100 years ago.
- Stock rubber line to the diff has suited when I've done it. Also with the R32 master the stock hard lines suit too. The front right only **just** reaches though.
But there are multiple ways to do it. I'm sure others will be able to help with other options.
Hen