Functional way of implementing DB access with additional logic

Question

Currently, my goal is to communicate with DB using CRUD approach. Between simple operation i may have some extra steps (additional business-logic which may throw some errors).

import cats.effect.IO
import scalikejdbc._

IO(NamedDB(MyDB) localTx {
  implicit session => {
   val x = for {
      a <- IO(select()) // Option[Something]  (1)
      _ <- IO(log(a)) // Option[Something]  (2)
      _ <- IO(insert()) // Something (3)
      _ <- IO(insert()) // Something (4)
      c <- IO(select()) // Option[Something] (5)
      r <- IO(fileSystemOperation(a, c)) // (6)
      _ <- operation(r) // Either[Throwable, Unit] (7)
    } yield ()

    x.unsafeRunSync() // (8)
  }
}).attempt.unsafeRunSync() match { // (9)
  case Left(value) => println("Error")
  case Right(value) => println("Success") // in reality i want to return some result here
}

The first problem comes in (2): i got error:

Error type mismatch; found : cats.effect.IO[Unit] required: Option[?] _ <- IO(log(a))

But if i log result of any insert ((3) or (4)) then all is ok. Probably, it's because of difference in result type Option[Something] vs Something, but i thought that it would be the same as this:

for {
    a <- Option(1)
    ....
}

The second question is how to correcly handle errors in (7) to rollback transaction? Do i have to use pattern matching and do something like this:

operation(r) match {
    case Left(e) => throw e
}

or i can throw error inside my operation and return Unit instead of Either[Throwable, Unit]?

Also, i have question about (8) and (9). Is it a correct way to start actual processing and handle any error or not?

I tried to do the same steps using this approach:

select() match {
    case Some(_) =>
        .....
        operation(r) match {
            case Left(e) => throw e
            case Right(_) => ....
        }
    case None => ....
}

But in result i got too deep match-case clauses and it was hard to read and understand. I'm new to FP, but i want to implement this in FP way.