Good gosh, so many incorrect answers, yes you can use heat to straighten dowels, I did it all the time when I was making dowel arrows. You can use heat on any arrow shaft and it works very well and will stay straighter than hand bending.
As for 3/8" dowels they will usually spine out between 70# and 90# and everything in between.
I barrel tapered a dozen 3/8 poplar dowels, 5/16" nocks and 11/32" point ends then sanded the middles to make a matched set of 55# arrow shafts. Very labor intensive, I wouldn't do it again but I ended up with some really great shooting arrows that weighed over 600gr