Citrus (Lemon Tree Health

Hello everyone. I have a question on doing what is best for a Citrus plant (Lemon Tree). This is a very sentimental tree to my wife.
The Lemon Tree is in a pot, and is very tall (we assume this is because it didn't get very much sun when it was first growing).
It is fertilized regularly, but has slight yellowing on the edges of some of the leaves.
The current worry is how many leaves that have fallen from it recently, especially around the middle of the tree.
It is now Spring and will be Summer soon, so it can be put outside and will get much more sun in the coming months.
However we were trying to decide what is best for the health of the plant, should we leave it outside and let it have lots of sun this summer.
Or should we cut it or trim it somehow? Or do something else.
We have researched how to keep citrus trees healthy but its hard to decide what to do best in certain situations
Is there any other information needed? We live in NJ, and the Lemon tree has been in a southern facing window all winter long.
What does everyone think?
Thanks in advance.
(Also please let me know if the photo attachments don't show)

 I think its a water/nutrition problem causing your leaf drop but am no expert.
With that much leaf drop be careful of full hot sun. Citrus has chlorophyll in its branches and can sunburn very easily, especially after being indoors so long. Maybe get it out under some dappled shade till leaves grow back in.
Branches need a lot of leaf cover before full sun for protection.

My potted lemon did the same thing (grew really skinny and tall then dropped leaves) and was much healthier when I pruned the top and started deep watering once per week. The soil should be dry a few inches down before watering again.

I put mine out last summer and it thrived, but I ended up having some issues with grasshoppers so I brought it back in.

Hey there and I am so happy to have found this recent thread. I inherited this lemon tree which is 9 feet tall, but I have 8 foot ceilings. I was wondering about using the copper wire to train the trunk to sort of bonsi it so I can still bring it in when it gets cold, I am in Michigan. Has anyone done or seen something like this? I have bent stems in the past for other plants and they were quite resilient.