Installing Tankless Hot Water System - Amp Questions & Using AWG 6 Wire with Current Tank

I'm looking into researching about installing a Hot Water Tankless system.

Specifically I want to install the following:

Rheem Tankless Water Heater 2.14 GPM 13 kW Self-Modulating Electric Wall Mount

It has the following power requirements: (RTE 13)

I had a few questions:

Lets start with the obvious, I'm not 100% my service is adequate. I have 100Amp service in a 1 Bedroom trailer that utilizes Electric Heat. I have 2 20Amp breakers dedicated to two different Electric Baseboards as well as the usual appliances. As it is a one bedroom it isn't often that many appliances are being used simulataniously, but I do want to be not tripping anything just by using hot water + heating the home.
Can my setup handle this hot water tank?
Here is an image of my breaker and the panel breakdown:

If so, perhaps this should be a seperate thread, but I'm just putting it all ine one for now....
Can I upgrade the current wire to AWG 6 and the breaker to 60Amp and hook that up to my current hot water tank system. The reason being I'd like to get the wiring/breaker setup so that when I go to install the tankless system it's "plug and play". I'm not sure if the different thickness of wire and size of breaker will matter if I am using a higher rated wire/breaker than needed. I'm guessing people just don't go higher because it costs more, but I'm not sure. #Hot-water #Electrical #Electrical-panel
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