We currently have the tech to save the earth from humans, to go green, to generate all our energy from renewables, to mass produce vat meats, vat cellulose(paper/wood).

There is already more than enough food to feed every person on this planet. And more then enough tech to do green farms, vertical farms, etc.

We have the tech to build a space elevator (railguns have been attempted in the past and were found to be impractical due to the high G force need to brake orbit, there is a company right now using it to shoot satellites into orbit , to colonize the moon, mars, and many many moons and protoplanets across this solar system.

We lack the will of the world to do it. Rather the political drive and economical will to do so.

To obtain propulsion systems to reach the speed of light or faster, there are several promising experiments involving warp fields (its a real thing) and ion propulsion systems coupled with nuke reactors to get us to the outer solar system and beyond. All the tech is ready to go, we just lack the funding to do it.

As for your magnetic fields, we currently use a model that has that takes into account gravity fields of all the objects in the solar system. We must navigate around these fields in order to meet energy savings and it helps speed up out movements.

Unfortuently using the magnetic fields as energy sources is finate to the stelar object in question. Take Earths, it only projects into space a mere 21 million kilometers. but a drop in the bucket in astronomical scales.