Will my Orange tree recover?

Hi there. I'm hoping someone will be able to help me with my orange tree which was bought for me for my 40th birthday, online two years ago at the end of march.  When it came, I opened the box to see a beautiful healthy tree with about 4 or 5 very small oranges on it.  The tree has been kept in my kitchen next to our bi-folding doors in a very sunny and warm spot for most of the year and in the summer is put outside. During winter I have noticed even though it's inside that it hibernates, coming to life at the end of march.  Our kitchen is very much like a greenhouse, under floor heating, loads of light, and nice and warm. 

Within the first two weeks I had it, the oranges had shriveled, turned black and fallen off the tree. Within another two months or so, despite me following all the care advice that came with the tree it lost most of its leaves and it looked like it was dying. It was obviously in shock. During that first summertime outside I think is when the damage was done, and very quickly the main stem turned brown and the branches died off.  I think in that first year I may have under watered it and allowed it to dry out too much.

Last spring I re-potted it and found the roots to be really dry and brittle, but I started paying much more attention to it and it is gradually coming back to life.  New branches had appeared low down from the original stem but much lower than they were before. They've slowly grown over the last year or so since that first summer and now they look very healthy but are generally large and beefy but very temperamental and weak.  Every time I put it outside it drops leaves, and gets sunburn. The leaves start to droop at first, then as the sun bares down, some fall off, and despite an intense citrus aroma, no signs of any fruit or flowers. With the tree in full sun, some of the leaves actually turn white, before going brown.

It's grown really well since then but the original stem above where the new branches come from is clearly dead. I feed regularly, every second watering with a citrus feed and try to only water from the bottom keeping the bottom of the roots nice and moist.  This appears to be working well, as last weekend I re-potted it again into a larger tub and checked the roots for signs of damage but they looked really healthy, much better than they were last year.  Certainly the lower half of the roots were heavier, softer and well nourished. The top half I guess from last year where it was in a smaller pot was much drier but definitely looked better.

I've been getting new leaves appearing over the past few weeks which has been really encouraging, I just want my little tree to flourish! 

After re-potting, I put it outside ready for the summer, but the weather has changed immediately after I did that and it's now much colder, the leaves are drooping already and the tree just looks sad when it's outside and I'm really afraid the same thing as before is going to happen. Maybe it's just a sensitive little home-bird?! 

I don't know if it's just a bit shell shocked from being re-potted again, or if the change of environment is at play.

My questions are numerous.  

1. Does my tree look healthy to you? Any ideas what I may have done to shock it?
2. Will this tree ever bear fruit? If so when? And how long am I likely to wait to see that.  
3. Should I plant the tree in the garden or now keep it in this one pot for the next few years to see how it develops, continuing to put outside in the summer? OR should I keep re-potting each spring? 
4. Has anyone got any opinions about what I might have done, or be doing wrong?
5. How can I stop butterflies laying their eggs in the leaves when it's outside. Last year caterpillars appeared all over it and ate many of the leaves! 
6. How's much water should I be giving it? I'm putting in about 1 litre a week currently. More if it seems dry or if it's hot weather.
7. Should I remove any of the leaves? Brown ones perhaps? 

Thanks for your help.
Steve