Actually, a goose question :-)

If there is anyway you could give him access to sunlight and grass for foraging that might help.  7 years indoors with no natural sunlight or natural forage may have caught up with his metabolism.

  And I might add he needs grit to help break down his food. and why lamb-goat pellets? I don't think your strange at all I have an indorr duck, but he can come and go as he pleases, so he gets as much sunshine and play time out of doors as he wants which is alot right now since he is 9months old and has girl friends outside. But I am a little worried about your gooses diet, I also have a gander who lives outside with the rest of my ducks and i can't imagine him eating anything you listed but the Romaine lettuce and bread which he gets in very small amounts. well he can eat all the lettuce he wants. but he does get to forage and I think that is very important for geese. And from the way you say he looks in his eyes and skinny I'd say he is missing something very important in his diet. I would def. add vitamins Theres a product called Poultry Nutri Drench that is got amino acids, vitamins and is made for our feathered friends. I give it to my flock not full strength but just to give them a boost in their water a couple times a week. If you could let him have some out door time I think that would help him alot. Sunshine is so good for all of us. And maybe get him feed made for water fowl or maybe Purina Flock Raiser pellets it's for water fowl also.

Thinking you are not strange at all, you love your little buddy, but as said before here,he needs to do natural goose things regarding his diet. He needs to graze on grass as much as he likes and I too not sure about your lamb pellets. Talk to a vet before he is too ill. Something here is missing I think. Also the home sealant is a real issue ver VERY TOXIC. call a vet. good luck, signed: fellow gooseaholic  :)

Joining in on the diet issue.

If you don't have a lawn, maybe you can get some fresh grass from someone who has one? My goose has mowed our lawn almost down to dirt, but I take my battery operated mower to other people's lawns and ask them if they can spare some grass.Most are happy with a free mowing, and the goose is exhilarated when I bring him back a bucket of freshly cut grass. Also, it keeps him occupied for hours, sorting through the bits he wants and the bits he doesn't want (like fallen leaves).

Also, do remember the grit. Without it, he can't process any food properly. Maybe you can keep a bucket of sand/gravel mix and let him have free access to it? My goose loves sand; he'll dig through it for a long time to find that perfect grain he wanted.

"Don't worry what people think. They don't do it very often." 

I cant help with the goose but your Not weird, in fact I envy you, im trying to get my mom to let me sleep with my rooster!!!!!!!!! I want agoose to imprint, hopefully this year ill get a nice goosey

 Flockraiser by  Purina or a waterfowl food (Mazuri  makes one) would be better. The lamb,goat pellet may have too much salt or an imbalance in calcium, ,etc. Buy "Storeys guide to Geese"  and they have  how to mix your own feed and what mineral balances they need.If you are feeding him a light colored lettuce it it not very healthy for him, also if it is white bread that is  pretty much junk food. Corn can make geese fat around their organs etc. They are grazers, you'd do better to feed him an alfalfa pellets if that is all they have. Maybe some good horse hay to nibble on. The best thing for him is good grass.... and they need some kind of grit/sand etc. to help digest food. The molting  could be because like an indoor dog, they don't have "seasonal" change so their system is confused. But I also think it  may be a nutritional  issue...(the insulation is water over the bridge, not  much you can do about it, it is either gone or in the tissues...) Be careful about grass or feedstuffs that have been sprayed with lots of  chemicals....

I give my entire flock Nutrena "All Flock" which is 18 % protein and intended for, well, all flock members.  I have chickens of all ages, ducks, and geese. 

Light lettuce  like iceberg is fairly low in any nutrional value - the "good" lettuces are Romaine and other, darker leafed lettuce.  I hang a green cabbage on a cord from a shepherd's hook in the yard a couple times a week for my flock and the geese love it.  They try to keep the chickens from getting any.... 

Salt is very bad for poultry.  A couple of Saltines every day is about all you can risk with your gander; if there are other salts in his food, it could be too much. 

I don't think you're particularly odd, even though I don't have house chickens, ducks or geese.  I do think your gander does need to forage, and he may very well need some nutritional supplements.  The suggestion of obtaining cut grass from a neighbor is a great one (just make sure they don't use pesticides on it). 

What we all REALLY want is a photo of your beloved gander!