If the twigs are green thy are alive and producing food for the plant. If they are crisp and brown they are dead and time to remove. I would pull the plant out of its container and check the roots. If they are really dry you will need to soak the tree in a tub until the root ball sink and has no air. This could take several hours or go quick. If the roots are soaking wet and smell of rot you will have to de earth the tree, cut off the bad roots and dip the roots into 10% chlorine beach/water solution to kill the pathogens. Then you will need to pot into a 5-1-1 type mix.

Do what Steve (poncirusguy) says. I hope it is getting more light than the light from the fixture above if not, move it closer to the window.

Does you pot have drainage holes?

Good question, Sunshine. I, sometimes wrongly, assume that people use pots with drainage holes.

Plant always inside .

At November when heavy leaf drop started i noticed plant hasn`t used much water so pot stayed long moisture. Now its fine again after new growth started using its water normaly.

I suspect is due i changed heigth of lamp and those leafs not getting enoutgh light like they used to have before and that caused stress. And those new upper leafs block light to lower levels.

Could someone confirm my guess? Dont know what else could be i have been using same setup soil and this lamp in photo, this is 3rd year and only this getting serious problem.

You need to direct one light at the soil and another one at the mid area of the tree for about 10-12 hours , slowly rotate the tree every three days around its axis, with three lights you will see a big change in growth.

I would not aim a light at the soil but parallel to it.

Should i remove dead branches and the ones that are empty now or should wait until spring?

I remove all dead limbs. Any green leafless twigs still have chlorophyll and make food for the tree. Leave them on the tree.

Steve

Added what i had Led growing light i used it when plan was small. Now it looks like that for the remaining few leafs. Will it work out till spring?

That should work well