kevin wrote:

Can anyone give me a hint as to how much load a very simply built howe
truss can take?

The load capacity will be as much a function of the joint assembly as anything
else. You'd be better off with a simple beam made of multiple 2x12s so as to
remove this complication from the task.

using a simple beam instead, even though it costs more... $60+ versus
some stock lumber I already have and can reuse later.

Small price compared to the consequences of failure.

Mike