Willa did! Willa's got bush for days and hella leg hair. He doesn't have much arm or chest hair though, due to how much of that skin is scar tissue.
Wojtech did not inherit ANY of that body hair. Willa jokes he can't spare any hair for his body because it all goes to his head. The most body hair he's got is a stripe of light fuzz up his stomach, at the nape of his neck, and on the small of his back.
Willa inherited Pat's hair type (wavy, dense, slightly coarse). Wojtech got his skin tone. They each have similarities in their facial structure, though Woj resembles their dad more, with his shorter nose and wider jaw.
Their biggest inheritances from their father are mental, both in the passing-down-trauma sense as well as their biological brain chemistry. The family anxiety and autism runs strong.

Yes!!! Willa really likes sitting in water. There's many bodies of water in the area around their house which they frequent. It's good sensory for him, the feeling, the noise, the visuals, the sweet smell of vegetation on the bank, the critters... he loves water... when he was a kid dad would get so frustrated trying and failing to keep him out of puddles lol. He couldn't resist sitting in them, clothes n all.
The twins go on more walks together in the nice summer weather, and they find a lot more stuff for Willa to snack on. Big crunchy bugs and berries, flowers and fresh greens, edible mushrooms, etc. They catch fish and crawdads, the few meats Willa likes. Spring and early summer is the twins' favorite season. Their dad likes late summer when it's the hottest. All of them are winter haters.

They wouldn't have to because Wojtech would do the job himself. If you stole him he would absolutely wreck your shit without any hesitations and probably kill you in the process of breaking away to get back home. He's an unsocialized dog with separation anxiety trained to fear strangers and bite on command. Even if you managed to incentivize him to stay with you he'd be extremely on guard, not eat or drink anything you give him, and not talk to you. He's just as distrustful and paranoid about people as his dad during the isolation era. Additionally his thoughts would be in a flurry of anxiety, not knowing what's happening to Willa while he's gone, it'd be hard to snap him out of that train of thought, he would not enjoy the time spent. Canon has no bearing on what can happen in your imagination though, the thought of taking him out for a good day is nice. It could happen in canon, but not while his dad and Willa are alive; the time period in which it would be possible for you to take him out for dinner is later in his life, in his recovery arc.