to NGA
I'm not seeing what you are identifying as spider mites. Spider mites are tiny tiny red insects (not actually insects but members of the spider family) that form masses of webs. That is what people normally see first - their plants being covered in webs.
Spider mites do like dust. Washing your cactus with soapy water (and rinsing well) is the best preventative. Once you have them, the best defense is soapy water.
It is a Cereus (maybe peruvianus or San Pedro), common name Night Blooming Cereus, not to be confused with Epiphyllum oxypetalum with the same common name.
Cactus don't need big pots - if its not top heavy, I would leave it alone. It seems to be doing good. If you do repot, consider putting it back in the same pot with fresh potting soil.
