planche pushups are hard.
Lie flat on your stomach with your hands at your hip-level. put your palms on the floor and push up. You will drag your feet on the floor which is normal until you get strong enough as to lift your whole body.

For dips, use ankle weights or a weighted belt.
One handed pullups...you can use weights as well, although I think you should just do more. If you plateaux, change them around, take 1 rep off each set and add an extra set or something like that.