I think you should try to pin down the oncology team about what they see the next month or two looking like. They will honestly, themselves, know how long he has got- they just won't want to tell you in case they are wrong or in case it upsets you and they know it isn't right to be too certain and nothing is 100%. But honestly hospice and nursing home staff see the process of moving towards dying, then active dying, all the time. Hospice bed planning means they are pretty sure where folks are on the journey. They will know what his weight loss means and how to interpret his mood, his energy level, his colour, his appetite.
I would also ask them about oxycodone and when they imagine doctors can add in things like oramorph. If he is scared they will not give a dose on time, he should be palliated more, I reckon - and have doses calmly and constantly so he is not worried, as well as anything else like anti nausea.
Does he have a cough or bringing up sputum from the tumour? That can be very unpleasant too and affect appetite so they can give something to dry up secretions but perhaps not until a bit later in the process.
I am sorry if I am being too blunt and clinical. I found it very helpful to have a sense of where we were with it all (he was the third person I had watched die so I knew the broad steps anyway).
There is a terrible time when it feels so difficult and demanding and you think how the hell can I do this, how can I manage, this isn't sustainable. But in all my experience that time is usually between five and twelve weeks from the end. And each few weeks, from now, there is an evolution and your role is different. The next 6 weeks might be about food and trying to get energy into him. Then two weeks following that might be about painkillers and making him comfortable and food suddenly doesnt matter. Then you have eight days right at the end where its a bedside vigil basically. (obviously everyone is different and e.g. a perforated stomach can mean you go suddenly within 12 hours- and cancer spreading can be sudden and rapid too- so it may not be as I am outlining- sorry if its too certain sounding).
So I guess I'm saying try and get a sense of how they see the next period of time going along. I'm so sorry if this is all a bit grim - I am trying to give certainty and gift you some small ability to plan, without trying to say I know how it will go exactly.
My DF had a period which felt like your current one. In this "steady state"- he was eating enough to keep going, yet complaining and panicking, didnt like the food, could still get up a bit and walk around but increasingly frail and fragile. I was speaking to him on the phone about every 2 days and going to see him for a day each weekend. In between times I had some admin calls to do for him - prescriptions and stuff, a hospital bed, buying tempting little things like protein mousse and saying hey try this milkshake etc - but I was NOT there for every meal. If that helps you as an example of someone else's experience, to help you balance what you think you should do and what you can do.
Good luck and take care xx