My fiancé and I have an Alsatian X St Bernard, Miniature Pincher X Yorkie, Jack Russel and we recently added a 10 week old Daschund pup to our family. I desperately need advice on the following PLEASE:
1. The correct diet for the pup (I heard that they need more calcium because of their backs);
2. How best to "potty train" him;
3. My Pincher sleeps inside our bedroom with us and I want the same for the Daschund (In future). But because of his lack of knowledge on where to "go" I have decided it best to keep him in the bathroom for the time being, however I've been putting both of them in the bathroom for the passed 4 nights so that the pup isn't alone - is this unfair towards the Pincher? (She doesn't seem to be objecting to it - she actually goes to her bed in the bathroom out of free will);
4. I've left him outside during the day for the passed 2 days now (both of us are at work the whole day) and he loves playing with the other dogs BUT there are pellets and meat outside for the other dogs and the pup just wants to eat everything he sees even though I feed him in the morning and evening. How can I best avoid him eating their food??

I'd really appreciate any advice!

1 A commercial puppy chow, almost any of them as long as it is AAFCO tested. Do not add calcium. It is counter intuitive, but too much calcium in the diet blocks usage of it causing joint problems. I would switch to an adult chow after 4 months the same as large breeds to slow growth and allow stronger joints and maybe spine to develop.

2 Much of housebreaking is not training the puppy, but making it easier for your puppy, you, and your carpet while its body to catches up to its instincts. At around 8 weeks when the puppy goes to its new home, the time from when it
Realizes it has to go, and when it can't wait any longer is a matter of
Seconds. Only time will fix that. You can hardly be expected to be attentive
Enough to avoid all accidents There is no sense punishing the puppy for your
Inattention. It is not fair to punish you either, but you still have to clean
It up if you didn't have the puppy outside in time.

Housebreaking starts before you get home with the new puppy. If you don't have
A crate, buy one. I prefer the more enclosed, den like plastic ones. Skip the
Bedding. At first it gets wet, and later it can be chewed into choking
Hazards. A wire rack in the bottom will help keep the puppy up out of
Accidents at first. They are available with the crates, but a piece of closely
Spaced wire closet shelving from a home supply place is cheaper. If you
Already have a metal crate, covering it may help. Just make sure you use
Something the puppy can't pull in and chew. Dogs that start in crates as
Little puppies, accept them very well. Never leave an unattended puppy loose
In the house. If nobody can watch it, put it in the crate. I suggest letting
The dog have its crate all its life.

Choose a command and spot you want it to use. The less accessible to strays,
The less chance of serious disease. If it is a female, choosing a
Non grassy spot will avoid brown spots later. When you bring it home, take it
To the spot and give it the command in a firm, but friendly voice. Keep
Repeating the command and let the puppy sniff around. If it does anything,
Praise it. Really let it know what a good dog it is and how much you love it,
And maybe a treat. Note, being out there not only means you can praise it,
But it also keeps it from being snatched by a hawk. If it doesn't go, take it
Inside and give it a drink and any meals scheduled. A young puppy will need to
Go out immediately afterward. Go to the spot and follow the above routine.
Praising it if it goes is extremely important. If it doesn't go, take it back
Inside and put it in its crate and try again soon. Do not let it loose in the
House until it does go.

At first it is your responsibility to know and take the puppy out when it
Needs to go. It needs to go out the first thing in the morning, after eating,
Drinking, and sleeping. If it quits playing, and starts running around
Sniffing, it is looking for a place to go. Take it out quickly. You will just
Have to be what I call puppy broke until it is a little older.

By the time most dogs are about 3 months old, they have figured out that if
They go to the door and stand, you will let them out. The praise slowly shifts
To going to the door. Some people hang a bell there for the dog to paw. If
Your dog doesn't figure this out, try praising it and putting it out if it
Even gets near the door. A stern "Bad dog!" is all the punishment that is
Effective, and only when you catch it in the act and are sure you didn't miss
It going to the door. Clean up accidents promptly. I mostly keep the little
Puppies out of the carpeted rooms. Still I need the can of carpet foam
Sometimes. First blot up all the urine you can with a dry towel. Keep moving
It and stepping on it until a fresh area stays dry. A couple big putty knives
Work well on bowel movements. Just slide one under it while holding it with
The other. This gets it up with a minimum of pushing it down into the carpet.
This works with even relatively soft ones, vomit, dirt from over turned house
Plants, or anything else from solids to thick liquids. Finish up with a good
Shot of carpet foam. Note, do not let the puppy lick up the carpet foam.
Once the dog is reliably housebroken, your carpet may need a good steam cleaning.

Many people strongly strongly push cleaning up all evidence of past accidents. I am slower to suggest that. Dogs will return top the same spot if they can find it. When you see one sniffing the spot, that is your clue to run it out.

3 Put the Dachshund's crate, the Pincher, and all in the bedroom.

4 This is a tough one. Free feeding works very well for some dogs. All day is too long to leave a puppy in its crate. It needs a break mid day plus another meal until it is 4 months old. Can you put the food up where the puppy can't get to it?

I am very glad you have given a home to some cross breeds. So many fine dogs are killed every day for lack of good homes. I have a 5 month old Lab/Golden cross now. She was deliberately breed by a dog guide school to give just the right personality. I was at the school recently, and the staff that saw her were very happy with her.