Yes, ET500 would make a good alternative to Araldite and could be used for all of the same applications. Given its fast cure, it's more similar to Araldite Rapid, rather than the normal slower Araldite.
As for using it without a mixer nozzle, yes, you can certainly do this. Again, it would be much like Araldite where you would squeeze out equal amounts of resin and hardener (A and B in Araldite world) and then mix them thoroughly on a clean surface. Squeezing equally is much easier using a dispenser gun, even when you're not using the mixer nozzles. The twin tube cartridges do come with a cap which can be placed back on to the tube. I don't recall if the cap can be accidentally turned around but if it can then you'd need to make sure you don't ‘cross it over’ when you put it back on the adhesive.
