The Bessa R3's will work fine with the 35f1.2. Focussing wide open is no problem, if you are careful. this is not a function of the camera(s), but the fact at f1.2 you have a very shallow depth of field. On the R3 the hood of the 35 intrudes into the 40 frames a bit (particularly when using the vented hood, the straight one intrudes less). The Bessa's have a short rangefinder base so you have to consider that.
Apart from my M2's or M6 0,56's I use the R4M with the 35/1,2 (the few times when I remove a 21 from it!). The frames are ok and the smaller "view" gives me less intrusion of the hood.
My suggestion is the R3M or A, depending on the amount of control you want to have over the exposure. The A's will incorporate light readings from spot lights/street lights and skew the exposure. On the M you soon learn how to use the EV setting to compensate.
The 35f1,2 is a bit of a magical lens. Very good performance and remarkably flare free. Remember. at f1.2 and with high speed film like a 1600/3200 asa film, the lens "sees" better in the dark than you do.