6th house is not for long term diseases, it is the 8th house which is for chronic diseases. The period of Saturn should only give brief and small diseases during its period. The 6th house is also for enemies and strong Saturn in the 6th house will give the native the ability to handle his/her enemies very tactfully. 7th house lord Saturn is strong in the 6th house, not good for marriage as it is the house for legal problems. When a person has strong 6th house chances are that god forbid if the marriage goes to the courts , the native with strong 6th house ends up winning the legal case in its favour. Don’t tell your life partner/husband ever about this thing in your horoscope.
Regarding retro the Saturn will get stronger results when it get retro in the transit or Gochar.