The engine weighs about 350kg. The whole aeroplane weighs in at 750kg.

There is no need for a complex and heavy reduction unit. The large capacity engine has a lot of torque and is therefore able to swing a very large propeller with a diameter of 2,8m. This gives a high trust and that is what matters. You wouldn't be able to stand anywhere near behind the aeroplane even with less than full power.

More blades do not help as they would need to be be shorter to absorb the same power while most of the work is done by the outer part of the propeller thus reducing efficiency. More blades are only needed is when they can't absorb the available power at the optimum propeller rpm within the maximum permitted diameter. The maximum diameter is mainly determined by the propeller tip clearance.

I think the reason for electrically heated suits is that it has an open cockpit. Blowing hot air at the pilot doesn't really help and a suit lined with hot water hoses probably wasn't very practical...