Hello Luce747,
This is a bit long because I have thought long and hard about whether or not to do this, so I apologise if it sounds rambly and everyone else can ignore it!
I have been following this post with interest as I too, have recently bought 2 sheep the same age as yours, ewes as advised by the lady that I bought them from. She advised against me having even a castrated Ram for all the reasons posted here by others. I, like you, would consider mine 'pets' on the basis that I don't intend to eat them but I primarily got them as 'mowers' for my paddock. I thought they could do me a favour in helping to keep the grass down a bit and I could do them one as they would avoid the abattoir and could live a long and very happy sheep life here. That's not to say that I don't respect everyone on here who breeds sheep for meat. What I do understand from them though, is that their primary concern (in addition to and not as a secondary consideration) is that their sheep live a 'happy' and full natural as possible sheep type life before they send them off to very well regulated premises, that also do their best to limit animal 'distress'.
Bear with me...I'm trying to present an 'intelligent' perspective (!!!) as you have asked very specifically for one.
My primary consideration when I bought my sheep was 'can I give them an appropriate, sheeplike, HAPPY home?' I gather they can live for in excess of 15 years if kept as pets (if I don't kill them from fly strike!). You have taken the trouble to ask advice on here about the 'health' of your lamb and have received responses from some very experienced sheep keepers (I am unqualified to help with that as, like you, only a newbie to this) but I am a qualified animal behaviourist. You have presented the very real, possible and 'happening' elsewhere options for sheep (and other animal) husbandry. I think what we do have in this country though is the excellence in animal health care and husbandry that now places sentience, the perspective that the animals have feelings and can be happy or sad in the environments in which we place them at the centre of the decisions that we make about how they should be kept. I realise that not everyone does this but they should. They may still appear 'physically' healthy but are we as confident as we can be that they are 'psychologically' healthy? This is EQUALLY important. Because if they are not, they will suffer. We may not see it but it will be there. They may still appear to function well but they have a 'right' if you like, to experience and exhibit natural behaviours as far as possible even if they are going to be culled at a later date. If they dont, there is a wealth of good quality, evidence based reearch that supports the fact that animals will suffer, even if someone didn't mean them to. Someone else on here has already mentioned the 5 Freedoms and you have said that you know about those.
You have mentioned a couple of things previously which I will just select here if you don't mind, to illustrate my point:
'My goats breed which I feel means they are thriving'. Puppy farms breed countless dogs from miserable, sick, depressed dogs who are kept in appalling conditions. They can still reproduce though. I am not for one moment comparing your animal husbandry or obvious concern for your sheep to this, I am only trying to offer an 'intelligent' perspective for you to perhaps consider your comment alongside. I realise that if you didn't care about him, you wouldn't have posted on here in the first place.
'If they can make adjustments twice a year then why not stay on dry?' Animals will make 'adjustments' to the situations they find themselves in to survive. This survival instinct is both for a physical reason (they don't have any choice) or a psychological one (it somehow makes them feel better..such as with displacement behaviours.. Feather pecking with battery hens...weaving and wind sucking in horses that are stabled for too long, persistent barking in dogs that are stressed etc..etc..)
'I bought him with a view to spinning his fleece'. For one thing, I wish I was clever enough to do that with mine! But for another, I wonder when you will be wearing a jumper made from his lovely wool, if you can always put your hand on your heart and know that it is a 'happy jumper' or if, on reflection, it actually might not be.
I'm not confident that this is exactly the 'intelligent' response that you were hoping for as it isn't specifically 'feed' orientated and I am braced for a cross reply (!!) I know that your enquiry was about 'feed' but you have in fact, opened up an interesting debate (a good thing) because feed is only one aspect of the holistic approach to the care of our animals. My intention has not been to criticise you in any way.
And finally, as you have spinning talents, which I do not (!!) and if you decide ultimately that a different home might be your choice for your lamb (if you don't eat him) I will have 2 fleeces that I won't have any skills to do anything with if you're interested! Otherwise, I have been thinking loft insulation.......!