Flaxen
I'll deal with that first. Retrograde is not the same thing as Detriment. The former is an accidental debility, the latter is an essential debility. An accidental dignity has nothing to do with sign placement but is related either to the position of the planet in a chart (house placement) or to it's position relative to the sun (and planets are seen to be retrograde at certain points in their solar cycle). Detriment is related to a planet's sign placement - when it is in the sign opposite it's rulership. Modern Astrologers tend to treat 'retrograde' as acting oddly compared to the planet's natural disposition. Traditional Astrologers, will treat 'retrograde' according to the chart reading - in a horary chart it might indicate a lost possession becoming found.
In a natal chart it's effect depends on the overall balance of strengths and weaknesses (bot accidental and essential dignities), in some circumstances, where the overall balance is towards the weak end then it can inhibit that planet's expression significantly, at other times it may not have an obvious effect at all, I tend not to put anything of significance on it at all but accept that it might show some minor oddities in behaviour.
Ah! Thank you. That makes a lot of sense.
If I were you, I'd drop Placidus for your traditional work - despite the fact it was developed in the seventeenth century, it was never used widely till after the end of the 'tradition' I would suggest either Regiomontanus, Alcabitius or Porphry. Porphry is easy to calculate on your own, if you don't have any software - simply divide the arc between Ascendant and MC into three equal parts and extend those parts across the chart to determine the 12th and 11th cusps and 5th and 6th cusps. Then do the same for the arc between Ascendant and IC to get the 2nd and 3rd and 8th and 9th cusps.
Just tested those out using Morinus software and they all give pretty much the same result. It shifts three planets into my 6th house rather than 2 of them being in the 7th. That seems to have quite an implication for my interpretations.