Since MFP is sedentary TDEE based, with exercise added later, you have to try to fool it to work with normal TDEE, with the Fitbit adjustments having minor impact but still reflecting your changing day.

What you need to do is pick a typical average week where you have correctly manually logged non-step activities so the Fitbit TDEE is best estimate.
You can do this in the past too, just need your start times for those past workouts, manually log them, and then see what Fitbit has for that week as average daily TDEE.

Now take that average week and average daily TDEE figure.
Divide by MFP's Mifflin BMR they use under Apps.

TDEE / BMR = personal activity factor.
Find the setting closest, not necessarily less, just closest, to your personal activity factor, and set MFP activity to that level.
1.25 - Sedentary
1.4 - Lightly Active
1.6 - Active
1.8 - Very Active

Set weight loss goal to maintain. Set exercise goal to whatever, doesn't matter, not used in eating goal math anyway. Save out.
Confirm you have Fitbit adjustments as positive and negative.

Now go to customize your eating goals, for your FitBit avg TDEE - 15%, change macros to whatever you wanted to use and other goals as desired, save out.

So now MFP has a TDEE figure close to your average Fitbit TDEE.
On days you do more or less it will throw in adjustments to your eating goal based on that TDEE. Depending on the differences in your rest compared to workout days, your adjustments should be rather small and plannable.

Disable on Fitbit side their option for estimated calorie burn, unless you really do forget to wear your Fitbit often.

You would still log lifting workouts, which may or may not give you an adjustment back. If it causes Fitbit to report a TDEE to MFP that matches MFP's maintenance figure (which you tried to get close to average TDEE), then no adjustment.

Just depends. You would merely look at your daily goal and eat it.

Now, if you are sure you could meet adjustments that always go up and some bigger than others, and still meet daily goals, you can select an activity level that is below your personal one.
But you'd have to be honest on that one. But that way you'd get less and smaller adjustments on rest days that are negative.

And yes, that is a lot of work. But it's because you are trying to sync 2 tools, and not using one of them the way it was intended, so it messes them up.

Why do you want to sync accounts rather than just keep an eye on the Fitbit TDEE?
It's a valid way of doing it, in fact the spreadsheet has a setup to do exactly what I did there and another option, because many ask for it.

I have been trying to coordinate my new fitbit I had for 2 weeks or so now. This is great to read these posts. Thanks.