I'll skip the usual "leave it to the pros" speech. I will point out, however, that code compliance is far more difficult in a "tiny" home than in a large home. The past few decades have seen the code greatly revise the number of required circuits, the types of circuit protection required, and has even got into the details of running wires and making connections.
I'll also remind you that tradesmen are far from being slightly retarded chimps with tool belts. A true journeyman has had extensive training in proper DESIGN. Have you even tried to talk to a real electrical contractor?
As for the load calculation: Your best approach is to get a copy of the latest "Code Check Electrical" booklet. The last pages address household load calculations in terms you should be able to follow.
Keep in mind that, even if your calculations result in a total less than 60 AMPs, current code requires at least a 100 AMP service for a residence. That means 100 amp wire, 100 amp panel, 100 amp disconnect, and 100 amp main breaker.
What's the difference between a "residence" and a "shed?" Most authorities will maintain that anything with a sewer line is a residence.
When you do the load calculation for your tiny home, you need to consider the source of your electrical supply. Whether the tiny house receives power directly from the power company, or if it receives power from an existing house, matters quite a bit to the details of grounding.
