stand off missiles

The Air Staff in the UK were looking at standoff missiles in the late
50s/early 60s. These would have been turbojet or ramjet missiles. They
were always objected to on the grounds of 'vulnerability'.

Can anyone answer some questions?

1. A ramjet missile travelling Mach 2 to 3 at 70,000ft.
(a) would this be vulnerable to 'conventional' SAMs?
(b) if it were attacked with a nuclear tipped SAM then:
(i) what would be the effect in terms of EMP on the defence? Would the
radars etc have to be hardened? and
(ii) what would be the effect on the ground below of a 10kT explosion
at 70,000ft?

2. Low level: how vulnerable would such a missile be to conventional
SAMs travelling at say M1.5 at 500 feet?

Thanks in advance,

Nicholas Hill