7th house is the house of spouse and 8th house is the family of the spouse. If you understand astrology you should know this. Now when 7th lord goes into the 8th house, it means that the inclination of the spouse is very much towards his/her family. You know girl or boys where they leave all decisions to the family.
When Venus is combust meaning it is conjoined with Sun, it is not good for marriage. In a horoscope it lessens the marital happiness and in a boys horoscope it means that his wife will be sick and have health issues.
You have not hear correctly 8th house is not the house of death, it is the house of Longevity. From the 8th house we check the longevity of a native. Having said that 8th house is one of the malefic house, other being 6th and 12th. It does not mean if 7th lord is in the 8th house means death to the spouse.
Jupiter is the karka for husband and its conjunction is not good with Ketu. If the boys rashi is 5th from girls Rashi there will be 9-5 Bhakoot dosha, which again is not good. You should get the complete horoscope matching done and then we can discuss in detail. Depending upon which planets are involved and overall strength of the horoscope.