Emergency Parachute questions

I need advice on a pilot emergency chute. I am only a pilot and know
nothing about parachutes. I need an emergency parachute because I will
be doing aerobatics in a Pitts-like biplane: required by FAA. My weight
is #140. The altitude I will be landing if I am unlucky enough to need
to use the chute is 5400 feet. I am considering purchasing a used
parachute that I would have inspected and re-packed regularly by a
professional Master rigger.

Is buying a 10 year old parachute like a Security, Softie, Strong...etc
going to be significantly less safe than a brand new parachute?
(Assuming it checks out as OK by the Master rigger)

Is there anything to watch out for?

Are there any special tests that I need to have done on a used parachute
to know that it is still safe?

If the red-line on the aircraft is 180kts, should I worry about the
parachute being rated to only 150 knots or should I assume that I will
slow down to terminal velocity in an emergency and will only need the
150 knot capability?

What other considerations should I think of?