Whenever I get myself in your position, I start with a full blown sanitation of my army. Every expensive unit carrying out garizon duties is scrapped. Other "back-up" armies are scrapped. Front line units are called back. Instead, I invest in cheaper defenses: forts. If that all isn't doing it, I release the most outer holdings (in your case in Italy and Egypt) and concentrate on getting smaller borders. This could be achieved by for example defeating the Armenians to get the Caspian mountains as border, defeating the Thracians to get the Danube, etc. These borders can be defended more efficiently, saving me money.