Back up your data. Brace for a crash.
(You should already be backing up important data in the first place.)
What Your Symptoms Mean
As suggested in this comment, we can best answer your question if you provide the full output of the S.M.A.R.T. attributes. You did provide other information that we can use to guess the condition of your drive, though.
I didn't find or look hard enough to find the manufacturer specification with detailed information about your specific hard drive (presumably with the model number
WDBFJK0030HBK), so we're further limited and can't be sure what you're seeing in S.M.A.R.T.
(See the first paragraph of this answer.)
If S.M.A.R.T. has actually counted reallocated sectors, then some sectors have already been found as bad, and an internal table inside tracked by the hard drive controller has remapped the bad sector to a spare one. If the Reallocated Sectors Count is 200, then bad sectors have been reallocated 200 times.
AcePL noted that it is unlikely that Current Pending Sector Count also has the raw value of 200.
You're probably confusing attribute values with raw values. See this Super User question or the following documentation from Hitachi for the distinction:
9.5.2 Attribute values
Attribute values are used to represent the relative reliability of individual performance or calibration attributes.
The valid range of attribute values is from 1 to 253 decimal. Higher attribute values indicate that the analysis
algorithms being used by the device are predicting a lower probability of a degrading or faulty condition existing.
Accordingly, lower attribute values indicate that the analysis algorithms being used by the device are predicting
a higher probability of a degrading or faulty condition existing.
If CrystalDiskInfo did label "Caution" on Reallocated Sectors Count and Current Pending Sector Count, then there probably have been remapped sectors and probably are sectors waiting to be remapped. (Further information here)
The reallocation of sectors is transparent to the rest of your computer. You would notice if files become unreadable (as part of sectors that can't be read after repeated attempts) or if you check the S.M.A.R.T. raw value of the Reallocated Sectors Count.
Once your drive runs out of reallocated sectors and writes start failing, S.M.A.R.T. will report an imminent failure. The same goes for failed reads, which you have been fortunate enough not to encounter yet.
Some hard drives (perhaps yours, too) slow down for reads and writes to try to improve the reliability of those operations. This could explain the reduced transfer performance that you observed.
Judging from the HDDRegenerator.Net documentation, it seems that "delays" are HDDRegenerator's way of identifying when the drive slows down for read operations or perhaps where sectors have already been remapped/reallocated.
It's not clear what the clicking sound is. It could be the hard drive struggling with writes kind of like how one would react if their pen were to run out of ink or it could be fragmentation causing the drive heads to seek rapidly.
You're fortunate to have a readable drive. You'd better back up all of your data soon. Make sure only to read from this drive and write to another.
Do not defragment before backing up. Defragmenting will perform both read and write operations on the same drive. Your drive may find bad sectors while writing or cause additional damage if there is debris floating around inside the drive.
Additional Information: Anecdotes
This Super User answer shows read errors on 24 May 2015. The drive worked fine after remapping unreadable sectors, but on 19 July 2015 during a massive write operation, its condition rapidly deteriorated as the drive controller realized that it couldn't write to many sectors. This is why I advise that you do not defragment because unwritable sectors can be lurking and outnumbering the spare sectors built into your drive.
On 01 April 2012, I noticed an input-output error on my 640GB laptop hard drive. I didn't have any S.M.A.R.T. monitoring set up at the time and was a novice at hard drive problems, so the issue crept up on me. A few months later, I made a Super User answer about general slow hard drive troubleshooting using that 640GB hard drive as an example.
On 25 December 2010, my previous laptop hard drive failed and started making a rapid clicking noise. About 5-6GiB of data became completely inaccessible, suggesting that a reading head began moving out of specification. From then on, unexpected clicking noises have been scary to me, which is the initial reason why I strongly suggest making a backup as soon as possible.