I concur with Geraint's suggestions of contacting the chief constable of the force that arrested your husband when he was 17-21. Be prepared to be persistent.
You may want to check the notes on the PNC
I recently posted on my blog.
Some particularly relevant links I include are:
* to the weeding and step-down of information policies which are currently governed by the MoPI Guidance - Step model - Retention Guidelines
(with the chief constable having the discretion to delete information s/he added). As far as I understand stepped-down info would not appear on the ACRO certificates used to get a US visa. Stepped-down rules depend on offences.
* to a decision
by the information tribunal about the retention of old minor offences by five police forces. This decision has been appealed by the police forces. The outcome of this case will be key to how the police forces handle this in the future.