I have never rewired a Sumiko. So I can add no advice for that part.
1)34awg is only a starting point. There are many of us that believe the smaller the better. I am using 44awg magnet wire, enamel coated. The clarity in the midrange is astounding. I know you said you like a warm sound, but I will address that later.
2)Copper wire is a good conclusion. I have never tried Silver, so can't comment.
3)Silk or Enamel; here is the hard part. The dielectric has more influence on the tiny signal than most want to admit. Silk is the best since there is no cotton coated wire I know of. A silk wrapped wire will have the least amount of dielectric smearing. At this point your need for a 'warm' sound is out the window. Good. Once you taste clarity, you would never go back.
4)Please invest in lead free, silver solder. Mundorf, WBT being two easy ones to get.
5)I will get a lot of grief for saying this next thing. WBT Nextgen RCA connectors (way too expensive, but the best I have used), with the Eichmann Bullets being the next best. IF XLR, the cheap Neutrik 'non' gold plated being the best of that family for me.
6)Keep the wire on the outside of the armtube for now. Try a few different wire's until you find your fave. Don't discount 46/10 Litz wire, cheap cheap cheap, sounds great.
7)Shielding may not be needed. For my system, careful orientation of the wires as they reach the phono pre get's rid of any hum. Non shielded cables sound best to me YMMV.