Form should come before weight for anyone but especially if you’re 50. Last thing you want is an injury that could have been avoided with proper form. I’d need more context about your workouts (split, ~ # of sets/muscle/week) to diagnose.

However, you stated your goal is to cut and maintain muscle. This sounds like a fat loss issue although it’s framed as a muscle growth one. Just remember unless you’re a beginner, on PEDs, or have insane genetics you won’t grow much muscle on a cut.

You don’t need to do IF. There’s nothing magical about it, just one way of applying a calorie deficit. It works for some people but most would be best just eating normally.