First you have to realize that bicycling is amazingly efficient. Sometimes too efficient. A human on a bicycle is the most efficient mode of transportation on the planet. It takes less energy to move a bicycle at 15 mph than it does to walk at 4 mph. If you want to build strength on a bicycle, one of the best ways to do it is to cut into that inefficiency by making the pedaling harder. A more aggressive hard pack knob at around 45psi will increase the rolling resistance...and decrease energy efficiency...by about 2 times over a slick road tire. Your tire isn't all that aggressive but the rolling resistance will be higher than a slick as well. If you really want to build strength, go to a very aggressive knob. They are much, much harder to push.

Thick, agressive knobs aren't there to protect the wheels. An aggressive knob is there for traction. What protects your rims is the volume of the tire. It acts as a cushion for impacts, especially at the lower pressures that mountain bike tires use. You want to run enough air to keep the tire from bottoming out and allowing the rim to hit the object that the tire is rolling over. The problem, however, is balancing the pressure. If the pressure is too high, the tire doesn't roll over objects but bounces off them. You start to lose control. On a road bike you would never hit as large an object as you do regularly on a mountain bike because the tire deflects off the object and throws you off line. Off-road, high pressures result in the bike bouncing all over the place in an unpredictable manner.

If the pressure is too low, the tire will bottom out and result in a pinch flat. Tubeless tires solve the pinch flat problem...no tube to pinch...but many people forget about the other part of the equation which is the tire bottoming out and bending the rim.

Spokes aren't protected by the tires at all. Nor are they protected by the rim. Because of the way that a bicycle wheel is put together, the spokes are working independently from the rim and tire. The spoke can...and does...slide up and down on the rim as the wheel rotates. At the bottom of the wheel, the rim deflects upward slightly and loosens tension on the spoke. The other spokes of the wheel pick up that lowered tension and spread it around so that the whole unit stays balance but there is a decrease in tension at the bottom of the wheel. Impacts can decrease the tension even more which means that the other spokes have to pick up the slack, literally. The spokes are protected from breakage by the strength of the spoke and the tension of the spoke on the rim but the tire has little or nothing to do with protecting the spokes.

Dual purpose tires are like hybrid bikes...they are asked to do two different jobs neither of which they do all that well. Your current tires are okay for what you are using them for but you'd quickly find their limitations in situations where a more aggressive tread is needed, just as you'd also find their limitations in terms of speed on the road. In mud, for example, the tire would very quickly become a slick and would act like a slick where you don't really want that. You'd likely end up face down in the mud at the first turn. You'd probably find them to be mostly useless in sand as well. They would just cut through the sand and leave you walking. Same goes for loose rocky climbs.

I'm sure that they will do what you want them to do currently but be aware that they have severe limitations if you want to do something more adventurous.