1)
From what age does a Meis render Tamei?
1.
Targum Yonasan: From the age the age of one month. 1
1
When he has left he realm of Safek Nefel. See Na'ar Yonasan who suggests that the correct wording in Targum Yonasan is 'Bar Tish'ah Yarchin' (a nine-month baby ? who is definitely not a Nefel).
2)
Why does the Torah insert the (otherwise superfluous) word ?le?Chol Nefesh Adam??
1.
Targum Yonasan: To include a (Rei?is of) blood of a Meis.
3)
How will we reconcile this Pasuk ("Shiv'as Yamim") with Pasuk 22, which wites "ve'Tamei ad ha'Erev"?