Hi everyone!  I was told to post here at the ask a vet section to see if I could get some answers

My 8 year old cat Salem one day started walking on his paw incorrectly.  A few days later he was chewing at it and I had him to the vet three times before they sent me to a neurologist.  There they found a mass by his heart and lung and the DR assumed that was the cause of the leg.  He gave him a few days to a week and sent me home with steroids and pain meds.  Its been past a week now and the only thing wrong with him his the leg.  The paw is dead, no more, cold and hard.  But he still uses the leg.  I have an e collar on him so he can not chew at it.  It had smelled before but Ive been giving him those meds plus Amoxi from my reg vet and now it doesn't smell.  But obviously the leg is no more.  

The vet I go to is a rather new vet and actually the practice I go to changes vets like tissues.  On monday night I am actually taking him for a second opinion with a vet who has been in the business for several years.  The specialist didnt want to do any amputation or surgery to test the mass because he felt he wouldn't make it and that we were poor and couldnt afford it.  He basically told me to just put him down.  I just can't see putting him down if hes doing so well (minus the leg)

Any advice would be greatly appreciated.  BTW it's his front left leg.  The mass is also on the left side.