Not necessarily, He after all got a huge damage when some girl says he is the bad guy. Then there is also this that implies that there would be no different from the mc. This happen when he fought the vampire lord for the first time...
Because they are white rice eaters beri beri is quite common especially in the past.
https://japanese-culture.sakuraweb.com/the-white-rice-diet-and-beriberi-a-historical-lesson-on-the-importance-of-a-balanced-diet/
For me no its is still alchemy , by definition it is still alchemy since changing one thing to another. It is reverse alchemy if plastic is made from processing wood. An example of reverse alchemy is changing things back to it original things like changing alchemized gold back into its...