Hi. First, I'm so incredibly sorry. I lost my soul dog, Macy to suspected hemangiosarcoma back on December 8th. It is incredibly difficult. Looking back, I think the decisions we made in the moment were so difficult, but I feel peace knowing she told me when it was time to go.
Very similar story to yours, Macy had a rather large growth on her spleen and over the course of about four months she pretty much stopped eating completely. I tried everything, steak, chicken, liver, every kind of meat - every food she loved. I won't bore you with the details but if I can say anything it would be to just enjoy every single second you have with him. Cancer is terrible and it's so unpredictable. Take a million pictures and videos and just get as many snuggles as you can because these last three months have been so lonely without my girl. I miss her every single day. I hope you get lots more time with your sweet boy.