Everything will go to your spouse if you have all of your children together. Where there are children from outside your current marriage, your spouse will get half your estate and the children will get the other half. There are special rules where you are separated from your spouse. There are also special rules where you have been living together.
You will need two witnesses unless you make a handwritten (holographic) will.
Yes. A holographic will needs to be signed and dated, but does not need to be witnessed. Be very careful if you try to do a holographic (handwritten) will. They are very difficult to do properly. People who feel they should have benefited from your will (or their lawyers) can often find ambiguity or fault with them. If your will is successfully challenged your wishes won’t be carried out.