Lonely dog needs flat toy ideas, and rawhide opinions; new "owner" here

Yes, flat toys, lol.
The Dog Biography:
I've "inherited" Coal, my parents' 12 yr old black lab (just guessing; he was a rescue at around age 4) now that they have both passed. He's sweet and well-behaved, but sometimes bites his tail or legs due to what I assume to be boredom or anxiety or loneliness, because my parents were home every day of his life, 24/7. My husband and I moved in upstairs from them last year (Coal has always known us very well), and currently he eats and sleeps downstairs where he is used to being, and we bring him upstairs with us when we're home. I only work out of the house a few days a week, my husband is gone most days. He's fine when he's with us, and overnight downstairs, but when we both work a couple days in a row and he's alone most of the day he's not happy. So....

The Goal:
I want ways to keep him busy. He loves flat things! I want to get him some flat rawhides because I think they might keep him occupied for a long time, but everyone says they're dangerous because pieces could swell in his intestines and cause a blockage requiring surgery. Fake rawhide treats get crunched and chewed within a minute. I attached a picture of a napkin that he kept busy with for a while. As you can see by the tiny pieces, he has no desire to swallow any of it; this was left like this for hours. He simply played with it, held it in his paws while he pulled it apart with his mouth, and left it there. Same with cardboard if gets hold of a piece, which he also chews on a bit, pulls apart, and leaves. He also would take a kitchen towel if he could, or socks, and try to do the same, but it's not as fun for him if it won't tear apart. He likes floppy small stuffed animals, holding them in his mouth and shaking his head so the thing flops around, hitting his face, lol. He also holds them in his paws and tears off an arm or something. Again, he leaves the smallest bits, so I don't know how concerned I should be about him swallowing things; he seems pretty careful not to.
Now I wonder if flat rawhides would satisfy him if it's ripping he likes.
Are rawhides actually ok or not?
Would he feel they're more like food, and want to eat them?
Can I just give him an old kitchen towel or rag and let him destroy it if that's what he wants to do? Or use rags to make my own disposable "stuffed animals" that can be torn up?
Would I be a bad doggy-aunt if I give him things like that?
Keep in mind he would be unsupervised; everyone says dogs should use toys and treats with supervision. Seriously? That's not realistic if the point is to keep busy while we're at work.

One thing I do when I leave him for the night is smear a blob of peanut butter inside a hollow bone and he goes nuts! He jumps up & down excitedly, but I'm not sure how long it keeps him busy for.

Any advice or tips are appreciated! Thank you!

What a handsome man! Coal looks like a sweetheart.

I can only give you my experiences so take that with a grain of salt. I used to give my dogs rawhide and never had an issue but I learned their individual habits before leaving them alone with the treats. Due to the advice coming out widely on not providing rawhide to dogs, I have changed my habits and provide my dogs alternatives.

One of my dogs in particular sounds similar to Coal in the way that the dog appears to be nervous or bored if they weren't kept occupied. I currently have a little dog who likes to take out her boredom on my wool laundry balls if I'm not careful to put them away properly.

The current favorites in my household include lambs tails, wolffish chews, and bully sticks.

Lambs tails - Some flatish, some round, Relatively cheap, easy on digestion, shortest lasting chew.
Wolffish chews- Flat, A favorite of both of my dogs. Can smell a little fishy once being chewed on. Hard to source at times.
Bully Sticks- NOT FLAT, Longest lasting, can be pricey depending on your source, can be tricky for your dog to handle at first due to it rolling around.

I would hesitate to encourage ripping up things like towels or rags because he might think he is allowed to rip up OTHER fabric items. There is always the worry of choking but if he isn't ingesting them like you said then you are most likely okay.

My personal risk acceptance would be to allow my dogs to chew on things that are edible, just for the peace of mind.

A trick that might work could placing that peanut butter filled bone into the freezer for a while. A friend who trains his dogs with kong toys would load them with peanut butter (and other things) and freeze them to make the enrichment last longer.

I think it could be adapted to a more Permie friendly way through utilizing a bone instead of a kong?

My dogs like black 'Kong' rubber bones with treats stuffed in the end, prefrozen like Timothy.
One of mine swallowed a rope pull toy that strung out through his digestive system
...$$$ later he survived.
So I hesitate about fabric.
Cow thigh bones are popular and stuffable, although possible tooth breakers.
Cow  patellas also popular although they can get gnawed down and stuck in the upper palate; I extracted one with needle nose pliers one time.

Pig ears and chicken feet are good chewables that also provide needed nutrients. Can be expensive in stores, though.

The only time any of my dogs have had problems with rawhide is if the wrong size or shape for them. The rolled shapes can be a problem that way. My big dog got a piece of pencil-width rawhide roll wedged across the roof of his mouth once, and it was distressing to him and hard to pry out. Then when he had a larger baton-sized roll he swallowed the last inch-long nub whole and it made him throw up. Never had any problems with the flat squares, though. Particularly now they make them with perforations.

Have you tried pigs ears?  They were the rage a few years ago I don't know about now ...

First, I'm sorry for your loss Kim. Coal is obviously also missing your parents. He won't know what has happened, just that his pack has gone. Labradors in particular love to look after their pack. Unless he can sleep he probably just won't be happy by himself. Is there anyway you can get him a companion to look after? It doesn't need to be another dog, a cat will do. Dogs tend to be very accepting of different people forms (2 legs, 4 legs all good).

Failing that probably something that he has to work at to get the food at will be best. You can get puzzle toys for dogs that they need to solve to achieve the reward. I've also heard of something like a lick mat which the treat (like peanut butter or yoghurt) is put in a nobbly plate so they can lick it for a long time without running out. You'd ned to make sure Coal wasn't likely to eat the mat too! This is a UK version, I expect you can get them in the US too:

lickimat