Regarding Dolgo crabs..I don't mind tart or even astringent flavour , and find that the best tasting apples are a mix of sweet and tart and other complex flavours....not so keen on sweet all by itself....like Red Delicious ....boring apple !.....I love russets because, although they are very sweet, they are also tart and malty and have other flavours ....which brings me to Dolgo crabapples....lots of comments about how they are only good for jelly......I strongly disagree, I only just planted my 2 Dolgo crabs last year and well, they are tiny, but incredibly delicious...they have wonderful sweet/tart flavour but also a tropical fruitiness not just golden orange colour, but also golden orange fruit flavours such as mango and passionfruit...they are delicious right off the tree in my opinion...they are tiny , dime size, or nickle size, but packed with flavour.

Hard to say for sure, even if you had a photo. In my orchard, that description would fit 'Callaway' - and it's a favorite, here, for fresh eating - though many of the fruits tend toward being a little bit pointy toward the blossom end, rather than fully round. Bears so heavily most years that it assumes a semi-weeping character. Good disease resistance and clean foliage. 'Evereste' is another good ornamental crab with top quality (if small) fruit.

Could be any one of a number of 'ornamental' crabs, even including an unnamed seedling, but two likely possibilities include 'Callaway'(that's what it would be here), and 'Evereste' - both fit that description, and the fruits are quite tasty.

Those leaves look like they have a Manganese deficiency. I don't know what ocean based nutrients are, but I know urine does not have enough manganese, or many other micro-nutrients. I'd suggest getting a complete citrus fertilizer made for container culture. Many hydroponic shops will carry this, or you can order online. Foliage Pro is very popular on this forum and also Osmocote Plus. I've never heard of citrus getting TMV, so I doubt it. Especially since it looks so much like lack of Manganese, which is much more common. As far as what type of orange, that's a tough one. Best I can say is that it's a Mandarin of some kind. Do you remember where you got it? Maybe the retailer will remember.