What is Sans' HP at now? I'd imagine it has to be higher than 1 HP to deal with the creatures of the foil
B- HP is something that molds and changes for monsters under different circumstances, I feel. It’s why Undyne didn’t kill Sans when she broke his skull; he had been very happy, previous to the Glitch. In Undertale, when you fight him during Genocide, his hope is practically gone, the lowest it can be. All that’s keeping him alive is the drive to stop Frisk. In Axetale, his hope had soared due to his happiness and his love for his family, giving him new life and new vigor.
As it stands now, his hope is very low, probably around 80 to 100. It surges when Aliza comes, pushing him forward to try harder and be better, but before her fall, it lies at one or two, heavily damaged by his cracked soul and the Hunger and the never ending night of the diseased world he lives in. He has significent LV, from killing and eating other monsters, but that bears no effect on his, or any monsters’, HP.