1) You never use all the available capacity on all your circuits at the same time. Individual lines may have a 15 amp limit, but the main circuit is limited to 100 amps. If you max out all your circuits at the same time, you will trip your house breaker.
2) You have a very unusual house if your range and your refrigerator are on the same circuit. Typically your oven has it's own dedicated circuit, often with a much higher rated breaker. You should confirm this. If your house is really set up like this, you should install two separate circuits, one 30 or 40 amp for the oven and range, one standard 15 amp for the refrigerator and outlet. (You should also consider getting a smaller microwave. No one needs a 15 amp microwave.) Your mains should be fine.
All this is just general guidance. House wiring is controlled by local code where you live. A local electrician can ensure you are compliant.