Home body fat scales are good for exactly what you're doing - measuring CHANGE. I use mine for the exact same thing. I don't need it down to the gnat's eye every week, I just need to know if I'm moving the right part of my body mass! One of these days I'll get a real number from my gym.
By lifting heavy you're very much doing the right thing! Muscle burns more than fat, and women can't get bulky like Ahhhrnold.
You're going in a great direction!
As to keeping the muscle… A great way to give your muscles the best shot at not melting with your fat, is to feed them by eating enough protein. You can think of this in two ways: making sure you hit enough grams of Protein a day (maybe by breaking it up into goals per meal) or by shooting for a particular Carb-Protein-Fat macronutrient ratio (which for muscle keeping/building reasons would be based on grams/protein anyway... but some find it easier to track).
Grams of protein to aim for /day is pretty straightforward. Sedentary adults should have 0.8g/kg/day. Weightlifting you should be closer to 1.4g/kg/day. I'd link sources but googling bodybuilding and protein intake should get you headed in the right direction. Bodybuilders have been figuring out the fat loss without muscle loss process for decades - after all, many people have great tone, but it's eliminating the fat that allows the muscles to show. SORRY… I digress (probably again… and probably too much
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As to macro breakdown of what you're eating... Think percentage of calories broken into Carb-Protein-Fat. It sounds like a pain but if you can use MyFitnessPal (which has a web interface as well as an app), SparkPeople (ditto) and I'm sure there's a few others... they will break down the macros for you. Added bonus for tracking what you eat.
What macro % breakdown should you go for? Here's where it gets a little fuzzy... some will say various percentages. Normally, if left to my own I will eat 70-15-10 (C-P-F) which is bad by any book... but not atypical for an American. Typical reccs for "active people" will hinge around 60% carb but IMO (I am NOT a nutritionist, I just read a ton) - even distance runners don't need 60%. Which, running is my hobby… and glycogen is another discussion.
ANYWAY... Body builders will recc 30-30-30 (with the extra 10 for slack) or 34-33-33 OR 40-30-30 if you want to split hairs… OR they will take the protein calc from above, look at the number of calories they're eating, and break the %ages down from there . IT's a bunch of basic math but some people can find it a bit much to scratch out…
If you're looking for a relatively easy place to start, a great target would be to shoot for grams/day. Take the 1.4 x (weight in kilograms) and you'll have it. For me it would be _165 pounds is 75kg x1.4 … which gives me 104g of protein a day. If you google "pounds to kilograms" a converter will pop up on google.
When I was first trying to increase my protein intake I was a bit panicked as to how hungry I would be. Protein is satisfying. Fat is also satisfying - just be sure to pick good sources. Lots of fruits and veggies - of course. You will find that the natural sugars in fruits will get you nicely forward that 40/30% carb area.
Good luck! Feel free to PM me for links or questions.
Best wishes.
~Becky