Cool ears is not in itself a sign of illness. To know if he has a low temp you need to take a rectal temp. In a bun that is eating, pooping and acting normal, cool ears can just mean the rabbit hasnt been moving around very much. Not moving around as much as usual can also explain the varying poop sizes.
Weight loss is more worrisome. It’d be good if you could weigh him in case he keeps loosing – unexplained weight loss is never normal in a bun that isnt very old, and he isnt very old.
It sounds like a good idea to have him sden by a vet on Friday. Sooner if he stops eating.
It could be that the loss of Blossom is temporarily making him a bit less cuddly. My Snöa was rather withdrawn for a few days after she lost her husbun. Even if Thumper and Blossom weren’t bonded, they lived near each other. He knows she’s not there anymore, and he knows you are sad and upset.
Here is a good video on how to take a rabbits temperature, in case you want to do that. It’s not very difficult if you have a fast thermometer and someone who can help you hold the bun. I’ve found this video very helpful when I’ve needed to take a buns temp:
https://youtu.be/YZd10Hk0maA?si=gq7PlTKs92mhz23Z