The new pics show the problem is worse than appeared in the earlier shots. Many shoots only have a few needles and some are completely dead so the problems are now approaching critical.
Fert regime you are using should supply enough nutrients to keep a tree healthy so much more likely the problems are elsewhere.
That appears to be a very small pot for quite a large tree. I believe that's called shoehorning and I can't imagine it is good for the tree. The shoots I can see seem to indicate it has been growing poorly for some years with abnormally short annual growth.
If you left much older soil on the roots at repot that's also a likely problem as the tree will have so little new soil to grow into in that small pot that the poor, old soil will likely have a much larger influence on roots and therefore health. I know that bare root pine is reputed to be dangerous but so is leaving large quantities of toxic soil in a pot. I know I get far better results when removing the majority of old soil from pines when repotting from poor soils.
I will also assume that for this repot you cut some old soil away leaving a ball of roots and soil then potted up with fresh soil under and around the old root ball. When new soil and old soil are very different in a pot it makes it really difficult for water to move from one soil type to another. I know I've seen cases where the new, outer soil was nicely wet while the old, inner soil was still bone dry and other cases where the situation is reversed and the inner soil cannot dry out properly. (I've done many autopsies on dead trees here over many years)
I would start off by making holes into the old soil part to allow water and air to move through that soil as already suggested by
@Paradox and hope that will give you some more time.
At the appropriate time of year repot properly and give the tree a decent sized pot to allow it to recover for a few years.
? H2O sounds good.
