2 - 8 months kittens- problems with toilet habits & stealing food

We have two 8 months old kittens and I really need help on feeding & toiletting.

They are part Maine coone, part British short hair. Generally very affectionate, don’t bite etc. which is great. However we are having issues with toilet habits and feeding.

Despite being toilet trained and them happily using their designated toilet, they still seek toilet indoors despite me trying to do the “put the toilet eventually outside trick”. We currently don’t have a cat flap, but I am sure if we had one they’d just come in to do their business inside. Equally over night specially they seem to want to poop in all of our bath tubs. This is frustrating as I wake up and spend a good time of my morning routine cleaning up after cats first thing and rather odd because their toilet is clean. (And they happily used the same set up the many other times). It’s like once one car started this habit now both seem to think tje bath tubs are prime spots for pooping. Sometimes this then also happens on random carpet areas- agin access to the toilet is there and it’s clean! How do I stop them going in various places? How do get them finally to go outside, especially when they spend a good chunk of the day outdoors?

They steal food. Badly. I wonder if I am underfeeding but increasing feed has also led to same behaviour. My toddlers sandwich, bananas. Milk. Nothing is safe. We have never fed them from the table, we have solid feeding times that we don’t away from and feed them in a specific place in the kitchen. Any idea if that’s normal? Yesterday we literally had a kitten stealing an entire sandwich (just after their main feed) ans obviously making the random poop situation worse.

I have never had cats before these two have had them now for 5 months but was hoping some of the issues may resolve by now (perhaps I assumed they grow out of bad habits)- so please be kind :)