Body water fluctuates constantly, so what you see on the scale might just be that and not fat gain.
This said, I would make two changes. I would ditch the protein shakes/bars and I would bin the squash. By trying to force macros in , you are forcing calories in. Don't be proteins obsessed. You are now looking at a diet for life. You don't like chicken, don't eat chicken. Like already said above, eat beans, lentils, chickpeas, tuna, salmon, cod, eggs, some but not too much meat, yoghurt, big plate of broccoli, .... And what do you mean by sweet treats?
I also think that 6000 isn't lightly active, but just "I am not bed bound and walk around" . Unless you lace up your shoes and go for an 5 miles walk every single morning, then the steps any counter measures are just a reminder you are alive. What I mean, is 10.000 steps in 1 hour walked at a fast pace that does allow you to talk but not sing is very different than 10.000 steps in 1 day.
Not sure where that number came from, but 1818 calories a day is a lot if you are trying to lose weight and are 5ft 4. Use a fitness coach for fitness, but nutritional needs are way more complicated than putting numbers on a website, especially when one is quite overweight. Your fat isn't as metabolically active as your lean mass and shouldn't count as much when calculating calorie deficit.