Is this the first time you ran Hard Disk Sentinel? SMART "Reallocated Sectors Count" errors indicate SMART thinks that block has or will have problems and safely moves your data before the block actually goes bad and your data is lost. Or that's the idea anyway.
If this is the first time you ran this, those blocks might have been in this state since the factory, and most likely, would never cause problems. But if you have run this program before, and now these are new errors, then I agree, it is only going to get worse. Time to backup!
If this is the first time running that program, then I also think chkdsk /r can help. And yeah, on a large disk, it can take overnight, or longer. Just let it run until it ends, even if it seems frozen. Then run your program again and keep track of new errors - while you start doing your home work and review some new drives, like another SSD.
Check your warranty. The drive may be warranted for 3 or more years.