Ronia Chart
I've approximated your chart as 1 pm (!3:00) 27th September 2012, Sofia Bulgaria. This is not exact as I have the Sun 2 seconds off the position in your chart and the Moon 33 seconds of arc from it's position in your chart. However it's near enough for me to work on without doing further maths.
I've attached my chart, as it shows the Terms and Faces of the planets, and I've made use of those in my reading. I've used Placidus cusps to keep the chart interpretation in line with your chart.
There are two key reading points here - did he receive your letter and if so, what is his reaction to it.
Your letter is Saturn in 29 Libra on the cusp of the eleventh House. The eleventh covers hopes and aspirations, so we know what your letter carries - your hopes for a developing relationship.
That you are vulnerable through this - you've initiated the mover and of course risk it being ignored or rebuffed - is shown by Jupiter in Gemini. Although still direct, Jupiter is about to station Retrograde. That your significator is weak emphasises the way that you have opened yourself up to rejection in the hope that what you will get is the opposite, a welcome response to your letter. So I don't think the weakness of Jupiter carries any more symbolism than that.
Will he get your letter and what will be the chain of events. This can obviously become very complex so let's try to keep the overview as simple as we can. Mercury (him) is applying to a conjunction with Saturn (the letter) and is separating from a trine to Jupiter (you). So you've had dealings with him in the past (which we know). The problem is that before the conjunction with Saturn, Mercury will sextile Venus in Leo. So we're not completely sure he's going to get the letter. However, Venus will go on to aspect Saturn so we have the possibility of a translation of light. As the square to Mars has already been perfected, Venus' next major aspect is to Saturn and this is perfected on October 3rd before Saturn leaves Libra. So my conclusion is he got the letter, though it probably had to pass through someone else first (as you reported that you had to pass it on to someone else because you no longer had his contact details, I think that this is the event signified by the Mercury Venus sextile. A sextile is an easy aspect and Venus is a benefic, furthermore the sextile has been seen as having a Venus flavour to it. So a good friend is indicated here.
What happens next?
Usually the Moon is seen as giving some idea of the flow of events.
The Moon's last aspect was to Saturn (your letter) just before it (the Moon) moved into Pisces (ruled by Jupiter). At the time of the chart the Moon is in the Terms of Venus and the Face of Saturn. As we know, Venus is the mutual friend, Saturn is the letter - further evidence that the letter is getting or has got to him.
The Moon's next major aspect is to Jupiter. The contact with the Sun in Libra is inconjunct, so I would not consider the Sun here.
So we have a letter sent and received. We seem to have a reply to the letter, in the shape of the Moon, coming back (possibly via the mutual friend).
The aspect to Jupiter is a square - so this signifies some difficulties, or obstructions. This could be delays in you getting the response, or it might not be the positive response you were hoping for. It might be non-commital, luke warm, or not see a resumption of your friendship as a 'good idea', or even that he's interested but you will have to wait because he's busy. It's very unlikely to be outright rejection though, I would expect that to show up by an opposition.
After that the ball is back in your court. I would say from the previous horary charts that you keep pursuing him (in a nice way) because if you drop it, it shows lack of commitment on your part, in which case nothing more will come of it. Lilly is quite clear that the matter can be perfected through a square, it's just that there will be delays and difficulties to overcome.
I think you will respond quickly and positively, as the Moon's next aspect after the sextile to Jupiter is a trine to Mercury at 17 Libra. This of course completes the process of letter, reply and additional reply.
That actually seems a quite satisfactory answer to the question, and I don't thinnk it's necessary to get bogged down by looking at the Sun (even though it rules his third). Though you will note that the Sun is in the Terms of Saturn (the letter) and the Face of the Moon (the reply)
Two interesting things though about the Sun. It's next major aspect is to Jupiter by trine (though it is not applying yet). The trine suggests a positive response, so if we did consider the Sun, then the Moon/Jupiter square would more likely indicate delay or obstruction in the reply getting back to you, or that he's interested but you will have to wait till he's free of his current activities (a possibility mentioned above)
The other intersting thing is that Jupiter is now Retrograde, though slow. So it is 'waiting' for the Sun, which sums up your position now.
The chart looks good and seems to spell out what's happened quite accurately, so let's hope that it spells out the future actions just as well.