I can see why the original Jeff did not appear now

"B) What happens to Mike and Kaylee
C) How does the meth lab get finished."

B is addressed in Breaking Bad and C we know it gets finished, guess there could be some throw away scene, where Mike hires some illegals in a Hardware Parking lot, but it's not really needed.

So to point A in your post, I don't think Cheryl will peruse things any further, I feel that story was done when Kim says to Cheryl:

"Cheryl, you were his wife.
You... You saw him every day,
you knew him better than anyone.
Maybe I misunderstood what I saw...
You would have known."

Then Cheryl excuses herself and heads to the powder room, it is at that point I believe Cheryl shows she knows that Kim is right she never knew Howard. I'd even argue that she knew that all along and that is why Cheryl was being so accusing as she was feeling guilty about shutting him out and thought it/she may have caused his "suicide."

Have to remember that we have known they have had marital problems for some time and have been sleeping in separate rooms, basically it's a cold and distant relationship (Kim knows this as Howard told her). Now forward a tad, back in episode 4 when Howard is talking to his therapist (when Saul takes his car) he says: "At home, things are more or less the same. It’s not any worse. I guess I should feel grateful for that. It’s like we’re deadlocked, Cheryl still won’t talk about anything important,” he then continued on mentioning he even tried tips from his therapist to no avail.

Then Episode 6 when Cheryl appears and Howard talks about Saul and not to worry he's handling it, she acts indifferent to it, then this happens:

Cheryl: I'm having dinner with the Appels tonight, so you've got the house to yourself.
Howard: Tell them I said hello.
Cheryl: I will.

Then there is a wide shot of Howard in the house alone looking lonely and bored, so honestly I think that whole bit with Cheryl at the Wake ended when Kim said what she said. Because Cheryl knew she really knew nothing about Howard at least in the time since Chuck's death when Howard became a depressed insomniac in Season 4 (it is slightly after that when Howard tells Kim that his marriage isn't going well). Also if you remember it was Jimmy who gave Howard a "kick in the ass" style pep talk that was the spark to Howard turning his life around and when Howard begun seeing a therapist. Which is why I feel he apologised in this season and offered Saul a job at HMM (thinking 20 step apology scenario), then the bowling balls happened and his wife was indifferent to it all as above.

tl;dr I could be incorrect, however I don't see the Cheryl storyline continuing on as I saw that episode play out as her accepting she didn't really know Howard and won't pursue Kim and Jimmy/Saul any more.

I don't think any of those three things need to be addressed at all.

Cheryl Hamlin may have had, or still have, suspicions, but they are of no consequence. Kim shut her down. She will either accept that she didn't know Howard as well as she thought, or she will go through life assuming Saul and Kim had something to do with his suicide, but that storyline is closed. There's almost certainly nothing more of interest for us to see, unless she tries to take some sort of revenge, at which point a new storyline opens up.

We know what happens to Mike and Kaylee because it's addressed in Breaking Bad.

The meth lab gets finished by Mike hiring new workers to finish it. Like the Cheryl Hamlin storyline, unless the writers decide to introduce new dilemmas, it's a closed loop.

The story that we need to be told is what we began to see this week: what is happening to Gene? We've got the entire backstory leading up to his arrival in Omaha. Now we need to know if he's still in contact with Kim, if his attempt to keep himself safe from Jeff the cab driver was successful, and how his story ends. Does he live? Does he die? Does he end up in jail? Does he get a happy or sad ending? Is Gene going full Saul now? Or was that a one-time step back into that persona to protect Gene? That's where the story is now.

Presumably we'll get a little more of the Albuquerque days, but anything we get will be new layers to a story we already know. We have no questions about that time period at this point. Better Call Saul has addressed everything about everyone other than what the final act is for Saul and Kim.

102000, very interesting point. It is strange how something can be right in front of your face and you completely miss it.

That image completely went over my head.

But he was so miserable as Jimmy. I guess I want a satisfying conclusion to Better Call Saul and I'm not certain what that is. I guess I would like to see him back with Kim, but that might be just too happy of an ending for a story like this.

I think there is a possibility that Jimmy, Saul, Gene dies, but regardless of the ending, I hope it isn't ambiguous.

That is an interesting point, but when I was watching it, I instead saw a longing to be Saul. He really wanted that garish suit and was pining for the old days.

Also, I think what 102000 pointed out is interesting and leading to something.