Merlin engine boost cut-out

This is one for all you Merlin engine experts!

In various Merlin powered aircraft, I see a boost cut-out/override control – from what I understand, if this is not pulled,pushed or otherwise operated, the boost will be limited to the 30 minute or 1 hour climbing maximum (for a Merlin III, for example, that would be 6 1/2PSI), and with the control operated, the maximum boost is available (for the Merlin III this was 12 PSI), until the boost drops off through increase in altitude down to the 6 1/2 PSI maximum.

Now – I have a couple of questions about this –
1. I read a note in a report that suggested that more boost than the rated maximum was available at low altitudes, and that it had to be held down to that limit by pulling the throttle back. Is this true, or is the maximum rated boost the maximum boost that can be obtained under any circumstances? I can’t imagine, for example, that any pilot who had a hostile aircraft on his tail would be too worried about any limits!

2. If the cut-out is not engaged (so the engine is limited to the climbing power), does the throttle operate in a linear way at sea level? I think the easiest way to explain it is – if I was flying at sea level with the boost override engaged, throttled the engine back to the climbing power (which would have the throttle say, 3/4 open), and then disengaged the override, would the boost drop to 3/4 of the climbing power, or would it still be at full climbing power, and the final 1/4 of the throttle travel would essentially be pointless?

I know that comes over a little convoluted, but hopefully SOMEONE will understand the question I am asking!