[Gitfiddlemann]

Hi Su,
Great to hear from you. Thanks for the feedback and progress report. I'll try to comment on your various points:

When I'm practicing only my right hand, no matter how good it sounds at 60 or 80bpm, it sounds so much worse when I add the left hand to it.

Likely a simple explanation: Both hands aren't yet coordinated (i.e. synchronized) enough at the speeds you are playing.

Here's my question: When practicing the triplets, (at slow tempo like 60bpm), with my right hand, do play the triplets with as much control as possible or do I play them freely?

I'm not quite sure what you mean by playing in control vs playing freely. There should only be one playing goal, and that is: to play cleanly (both hands) and with good tone. That usually means in control of things, both hands playing in *coordinated fashion. Most especially in a piece like this.
You’ve been at it a while so by now you must have the piece well memorized.
In fact, when I last posted, I wasn't intending for you to practice improvements in your control just by focusing on one hand.
What I meant was for you to find a slow tempo, e.g. 60 bpm, where everything (both hands) is working out as it should, i.e. clean execution + good tone.
And speed up from there. Don’t practice each hand for speed, independently. I mean, you can if you want, but it’s not the most time efficient way of practicing this tune imo.

I’m guessing that right now, your right hand is likely better at handling the quicker bpms, and when your left hand gets into the action, especially for the trickier chord fingerings and fast strums at the beginning of each measure, it's impacting the overall synchronization of both hands if you're going about it too fast.

So, don't over complicate things in your practice. Just find a tempo (be it 40, 50, 60 or whatever) where you're playing the music, and are in control.
That means that both hands are playing in coordinated fashion, and in tempo. With good tone. Clean execution.
Stay there and get used to that.
Then, notch it up incrementally, using the metronome.
Nothing should be morphing from "in control" to "freely". It should feel and look the same, only faster.
Remember too, that the entire piece is an exercise in dynamics. You have to incorporate that aspect too at some point.
Let's face it. This is an extremely challenging piece. You picked a good battle.
But you obviously love it, so stick with it. You don't have to reach virtuoso speeds (imo) to make this piece sound wonderful and a treat to listen to, and feel rewarded by it. And slower clean will always beat out sloppy fast.
Also, you're not wasting your time at all. Just working on the piece will benefit your technique for other material.

Note: April until now have all been spent on these triplets. I could have learned a few intermediate and or solid pieces by now...and that's the dilemma I'm facing right now. Do I keep toughing this out or do I put it on the back burner while learning or re-learning new and old pieces? I know you can't answer that for me but any words of encouragement would be greatly appreciated.

I was going to make that point as well. When working on something so demanding, you really need to diversify your practice and allow time for different material. At least I do. Otherwise, it can get overwhelming, and start affecting you negatively.
So, definitely. Play other things, fun things. Set Asturias aside for a day or so. It might even be beneficial.
For example, if you want a much simpler piece that is well written and emphasizes triplets, why not give Andrew York's "Snowflight" a go. It's simple enough, but can also be challenging at the allegro tempo. And it's appropriate for the time of year.
Just a suggestion. I'm sure you can find your own good music that is not so taxing to lighten things up.
Also good: Pick some studies that mimic the techniques that Asturias demands of you. There are lots of those in the repertoire.

Lastly, I find your enthusiasm for playing, and for this piece in particular, to be a great asset. Even if you do give it up for a spell, don't even worry about it. Sometimes, a break can work to your advantage.
As long as you enjoy picking the guitar up to play, you'll be fine! Stick with it.
Let me know if you have any follow-up questions.