All powders are abrasives which slowly remove the surface from silver articles and wear fine chasing. A liquid is far safer for cleaning. Use a fine brush for removing dirt lodged in engraving but never scrub. A silver dip is an excellent preparation for all silver cleaning. All repairs to damaged silver should be undertaken by a reliable silversmith.
Strong nylon serves as an excellent support.
The tapestry can be mounted on nylon net without causing any harm. As tapestries are usually of considerable age and value an expert should be consulted on cleaning and the various methods of protecting the material against ravage by moth and other infestations. This is of utmost importance and should be attended to immediately you acquire valuable pieces. Loss by theft or fire may come as a great shock, but at least you will receive financial compensation to soften the blow.