Your worry is understandable. All of us have worried about numbers dropping dangerously low when we are new to this. Even normal numbers seem scary
For now he doesn't seem to going anywhere below 250. The rationale for not hanging on to a dose is that if numbers aren't where you want them, there's a tendency for glucose toxicity to develop. The term sounds a lot worse than it is. What this means is that your cat's body gets used to being in higher numbers and treats it as the new normal. This makes it harder to get the numbers back to the real normal. TR enables you to get to a good dose sooner - helping you to break through any glucose toxicity. For a cat seeing glucose toxicity, a 0.25U increase once a week, might just not cut it.
The Libre also reads much lower at normal/lower numbers. We therefore ask caregivers to verify these lows with a regular meter.