I agree - he needs a feeding tube if he wants to heal and fight this thing he needs a lot of nutrition - protein in particular and not necessarily meat based. There are other things out there other than ensure, that have more nutritional punch and higher protein. Try making him a shake daily with fresh fruits protein powder and veggies (even a scoop of veggie greens if you can) he can have a few daily - add flax, and make sure he gets a lot of fluids.

Chemo will not cure this type of cancer and lung mets are hard, for this you should have him at a comprehensive cancer center they take a team approach to his care, from nutrition to radiation oncologists to seeing that he sees the right type of dr. At this point I would push to find out how involved the mets to his lungs are - if its just one nodule and they are certain it's metastacies from his skin cancer then they may be able to surgically remove it - there are also clinical trials available at a comprehensive cancer center. Christine generally posts a list of those - find one close to you and get him in there. Hugs and best of luck.