Yes there is such thing as stubborn fat. There are different fat types. Brown and white fat for example. They behave differently.
Also fat has saturation level. Fat can be harder or softer, differing in density.

Usually if the part of fat is getting more used up by your body, you can feel the fatty part of the body to get softer.
I notice this especially for my calf and buttocks.
Before those parts become toned, the fat surrounding the muscle usually become softer first (from quite solid).
Maintenance calorie wont change much I think, unless you lose weight drastically.
It's just how human body works. The lower your body fat percentage is, the harder it is to lose fat.
Those remaining fats usually more dense and complex. Different than those flabby, soft fats.

Im not against your recommendation. Im just saying if your progress becomes slower, its very very normal.
You can see this with very fat people doing keto. They lose fat really fast at the start. Not talking about weight (which could be influenced by water weight), talking about fat, as in waist size.
But then when the progress becomes slower, they panic and wonder if they did something wrong.

Increasing activity is fine too. Increasing caloric deficit.
But increasing your patience is also viable.