Re: Improve HSPU and Dips ??
A HSPU generally good dipping strength. This is because it is more tricep dependent than a dip.
However, a HSPU from HS to your head is really only a partial ROM HSPU. Figure 50-65% (depends on arm length). This is assuming a roughly shoulder width HSPU and not using really wide arms to decrease ROM.
Stomach to wall is more transferable for free standing HSPU on floor, parallettes or rings. They also tend to be a bit more difficult.
Since you are only able to do 1 or 2 HSPU, you could try a volume approach spread out through the day (GreaseTheGroove), or you use a slightly easier progression to build more volume.
If your dip numbers are weak so are your MU. I'd guess though you can do way more dips than HSPU so a volume method could be used that isn't necessarily GTG or spread out the day. 3-5 sets of dips for max effort or some percentage. Sort of depends on the number of your max dips.