I can’t find any source showing the context of the 30-35% claim from US Intel. I can’t even find a reliable source of the US estimate of how many fighters they have. The last public numbers from US intel in January had much more detail and said 20% incapacitated, not 20% dead. A jump to +30% of Hamas fighters dead now seems beyond implausible. Especially because USA has also said they don’t independently track deaths in the region, they rely on local numbers.
Different Hamas officials have made different claims about their losses, and all the sources seems vague. It’s been reported as 6000 - 8000 either lost (could be casualties including injured survivors not able to fight) or dead. And some of them deny the numbers entirely.