i usually adopt our rats at 3 weeks old... I give them shredded wheat soaked in normal milk as well as left overs and about anything we eat as well as rat blocks. Egg whites, and a bit of meat or fish as they want it will help them grow but mostly young rats will pick and choose the foods they need most. Young rats grow fast and need a lot of nutrition... With the 2 week old rat we adopted we used powdered KMR formula. Seriously, don't overthink this, rats eat just about anything we do and young rats are just like human kids... They can eat more calorie, fat and protein rich foods than human adults. By 4 weeks old they can live on rat blocks, if they had to, but richer human foods won't hurt and will likely help.
To be honest, rat pups are really pretty smart, they don't usually swallow things they shouldn't... That doesn't mean you should expose them to toxic plastics... you most likely shouldn't expose your kids or yourself to them either. but just because a rat chews something up, doesn't mean it ingests it.
Last night, our big fat older rat Cloud was dumpster diving the kitchen trash and being particularly loud about it, she hasn't done it in a long time, but I remember when she was a pup and a young rat, she hardly ever ate anything she didn't find in the trash. Now, she more or less asks to be served leftovers and other human foods... I don't think she's ever eaten a rat block in her life. And Misty usually goes through the trash before Cloud can get to it nowadays... You might guess that our rats live pretty much free range in the house and somehow they don't get themselves killed.
We had a part wild rat long ago, and she actually lived outdoors on her own for a summer... I was amazed how competent and confident she was so we tend to treat our rats somewhat like rats. I'm guessing by some standards it might seem like neglect or even abuse... but our rats thrive and flourish and become very independent. They become family members rather than pets. There's a real tendency to pamper and overprotect rat pups, and there's nothing wrong with that, but always keep in mind your rats are.... well they are... actually rats. And rats are the second most successful species on earth and they are built to survive and thrive where nothing else will.
Once our precocious pup Max decided she wanted to eat before everybody else so when our backs were turned she jumped up onto the stove and singed her whiskers... she never did it again and Fuzzy Rat could strip the insulation right off both sides of an extension chord without ever getting a shock. Unfortunately that could get a little shocking for the human that didn't realize the wire was stripped on both sides, but rats are very fast learners and somehow they are naturally able to not get killed even when they are being reckless (most of the time).
It's fine to be protective and careful... but don't get to panicky. Sometimes you just have to have a little faith in your kids and rats.