When you say your calories have stayed the same do you mean from the very beginning or the last 5 months?

Did you at any time override mfp calories? When you do that, it won't recalculate and auto drop calories as you lose. Even if you haven't strayed from the "guided set up" in the goal feature, I have read that there have been glitches so you might want to go back and re-enter your stats under guided set up if that's what you've used before.

If you're eating the same calories as you were when you weighed 60 pounds more, your loss would be slower.

I too wouldn't pay much attention to MFP'S exercise calorie burns in regards to "10 pounds/month". I've read that the the strength training option under cardio is pretty in accurate because it has no way of knowing intensity, reps, sets, etc. If you're using the actual strength category, you have to enter the calorie burn so that would be your overestimate. The former applies to calisthenics. In regards to 20,000 steps is that 20,000 more than you previously did?

When I used mfp's walking estimates, they were by a time period versus step count and weren't far off meaning I kept losing as expected but an hour @3.5 MPH is only a couple hundred calories for me. I used it as a "cushion" because I didn't weigh and measure food.

5 months is a long time to go with only 1 pound/month based on previous history. I'd revisit your settings and make sure your stats are accurate.

Short version:
1) tighten up on logging? An unpopular response and unnecessary if someone is actually weighing and measuring all intake (and using accurate database entries).
2) dieting too long? A refeed or diet break may help.

It appears you have been consistent for 15 months with exception of the added exercise so your current 5 month results are a bit confounding to me as one who has effectively lost weight via controlling calories and following MFP guidelines. CICO. Low Carb. My weight loss phase was 53 weeks and fortunately consistent. I admittedly have a hard time grasping the idea of "I'm eating at a deficit and I am not losing weight" (if one does not have metabolic issues coming into play) so please don't be offended by my question of are you weighting and measuring food. I don't think you addressed that specific "thing" in your posts.

My thoughts result questions which don't have to be answered but I'll pose them.

1) Do you weigh and measure this high fat/keto food you are eating? I ask that from the perspective that I wasn't a person to weight and measure during weight loss but my plates we full of lettuce and other low calorie foods (averaged 128 carb grams/day. I began weighing and measuring food with my 52 week keto trial (for reason other than weight/management) due to high awareness of calories in fatty foods and sadness over the visual comparison of (lack of) volume on my plate. I still do much more weighing and measuring now because I eat high fat and I've still not become accustomed to or accepting of tiny little portions. I am an over eater. If you're not weighing and measuring, "the 1300 calories" you put on your plate might have been effective for the 1st 10 months but with a loss of 60 pounds the "1300" might actually be maintenance now (implying it might be greater than 1300). Stress from added exercise compounds the issue of not losing or losing more slowly.

2) When you say "redid my TDEE" was that somehow via MFP? MFP does not use TDEE. It uses NEAT. The question is for my clarification. There is a difference. You can get something close to TDEE via MFP if you enter "maintain" and an accurate "level of activity" in. NEAT excludes exercise. TDEE includes exercise.

3) Is 1700 calories your NEAT or your TDEE? Is it the amount you should eat to lose X per week with exercise not figured in (NEAT) or is it maintenance calories for current weight including exercise (TDEE)? It is somewhat irrelevant (perhaps) given you're eating only 1300 calories which is a deficit based on any of the scenarios. So that would take me back to the "weighing and measuring" aspect.

Aside from those specifics there is always the thought that due to increased activity you could be maintaining water from minute muscle tears but 5 months? Not so sure exercise would have that much ongoing impact since water retention in the case of exercise/muscle tear is generally considered temporary. I have little personal experience with this. Admittedly, I don't exercise with much intensity so rarely have much muscle soreness though I have on occasion.

The other thought is 15 months is a long time to be dieting. Refeeds and Diet Breaks have become popular/heavily researched and there is scientific evidence indicating their effectiveness. More anecdotally, I can't tell you how many times (though it has been a lot) folks here have posted that they were frustrated that the scale hadn't moved and they binged or way overshot their calorie goal then posted a day or so later that their scale finally moved downward. Go figure. A single day of excess is not specifically a refeed or diet break (as refeeds/diet breaks tend to be defined) but there are these anecdotes of a "one day thing" being effective. Same is true of the reverse (a fast). I personally favor the refeed (to maintenance calories) idea. I like to eat and fortunately have not experienced a need for either related to weight loss so I have no experience with structured refeeds or structured fasts. I just know of them.

There is a very lengthy thread in the General Diet forum on MFP: "Of Refeeds and Diet Breaks". Much of the research (links) is on the first few pages of this very lengthy 180+ page thread. I think it is currently on the 4th page of "General Diet" unless someone has bumped it with a post in the last hour or so. I follow it out of interest in the subject.

You mentioned "upping carbs". I know of at least one person (@DietPrada ) who indicated she upped carbs (vegetable carbs) and her weight started to drop. My memory might be wrong. Her interest stemmed from a desire to decrease saturated fat intake due to health markers. The increased weight shedding through upping vegetables and decreasing fat was an unexpected benefit. Again, if my memory is correct. She was/is keto for 4-5 years.

My personal experience is that when I ended my Therapeutic Keto experiment and went from < 20 carbs total to ~50 total, it was awesome! "OMG! Look at this lovely salad or pile of asparagus and I'm still under 50 for the day". It was a stress reliever, really. It more in line with how I "like" to eat and has not lead me down a slippery slope. I digress...

Sorry so long. It is just "stuff" that I've read and may be a catalyst for your personal research in finding a solution to why your would lose 6 pounds per month for 10 months then only 6 in the following 5. I'd be questioning it too and searching a solution. KUDOS on your loss thus far AND your tenacity.

Gets award for longest ramble...