Concentrate on the Pentax, for now. Get a tripod and a cable release. Find out where you can get some fresh Ektachrome 100 or Fuji Provia 100F and get it processed (just developed, not cut and mounted). Quit trying to take landscapes. Take something reasonably close without any sky in it, preferably with lots of detail like a street scene.

I think you have light leaks in the Minolta and, probably, exposure issues. These are aggravated by trying to take pictures that appear to involve a lot of atmospheric haze and exceeding the film's exposure latitude by trying to combine sky and terrain using an averaged meter reading and no compensation.

Your Minolta has a fresnel focusing screen in the center for fine focusing and it should be clear when you are focusing on your subject. It also has a split image which should be aligned to indicate proper focusing. I am not familiar with the Pentax, but, hopefully, it is similar. Use a tripod and a cable release to allow you to focus precisely and not disturb the camera when you release the shutter. Bracket the shots to give the same aperture and three different shutter speeds for each, one at the metered speed, one one stop slower and another one stop faster.

If you cannot use slide film, use black and white. Use C-41 process B&W film if that is all you can get processed, but leave the color negative film alone for now. What you want to do is eliminate as many processing problems as possible and make any such problems as obvious as possible. Slide film is better for this because the exposure latitude is narrower, the color and contrast are not subject to problems in printing and metering errors show up faster. However, trying to take the kinds of photographs you are now with slide film and no compensation will just aggravate your problems.

If you can, get a light meter that reads incident light. If there is a large difference between it and what your camera is reading, use the incident reading to set the aperture and shutter speed manually for the exposure. Last, keep the light behind you--no shooting into the sun.