What you are describing are not problems with the filter itself but with the multivalve, which is usually a repairable item.
Gauges are usually easily replaced as long as its threaded nipple is a standard size. Shouldn't cost much.

The leaking of the valve is most likely caused by a worn-out or damaged "spider gasket", a large rubber O-ring that looks like a spider web. There could be other problems with the multivalve, such as damaged springs or internal chamber walls.

Carl