1) When a significator (in this case Venus) is about to change signs, what does that mean?
2) Would jupiter be considered combust in the chart, or is it protected because it's in exaltation?
3) In the second chart I made, Jupiter (me) is angular (10th house). I read on another website that this means that this person (me) is haughty. Can you read the emotional state of the querent in a chart?
4) Mercury (me) retrograde: does that signify a change in mind? I wanted so much to get to know him, but after I felt like I was being avoided, I've told myself I won't interact with him. Is there anything else a retrograde could signify (not necessarily this chart, but in general)?
1. I would think that it would depend upon how changing sign affects the significator. In this instance, Venus changes from being dignified as daytime triplicity ruler of Cancer to being peregrine or without dignity in Leo.
So answering your question narrowly, I don't see this change of sign as indicating that a good change may be in the offing, as if, say, Venus were moving into Taurus or Pisces.
2. My understanding is a planet in its dignity or exaltation neutralizes the effects of combustion. As an aside, in this instance, Jupiter is also moving out of Sun's influence as Sun separates from Jupiter. This places Jupiter nearer to the area described as only under Sun's beams, rather than in the more intense area of combustion.
3. I believe you/Jupiter in Cancer might possibly have been described as haughty because planets their exaltation are thought by some to suggest exaggeration. When signifying an individual, it might be said that an exalted planet would have an exaggerated idea of themselves [haughty?].
Overall, though, I do not believe that horary is meant to describe inner processes or emotional states of individuals, but rather is geared to describing outcomes. Others with more experience may be able to shed more light on particular matter this than I.
4. Retrogradation usually refers to returning or going back to, repeating. In this instance, it currently indicates your attracted to, drawn to him. To my knowledge, retrogradation is interpreted pretty much like what it looks like. Ultimately you/Mercury will change direction, but I think that will be when you lose interest in him.