If the car was in your husband's name he doesn't need your signature to sign over the registration at the DVLA. Forget about any criminal offences he may or may not have committed as you'll never be able to dredge up the evidence to prove it.
Get a written report from the garage and then advise your husband that, unless he collects the vehicle within a reasonable time, you're scrapping the vehicle as it is of no value and unroadworthy. Then advise your divorce solicitor - forget the amicable bit, that's just a ploy by your husband while he bleeds you dry or treats you like some half-wit. There is rarely such a thing as an "amicable" separation where there is a third party involved.