With such a large percentage of the pond 5-6ft deep you will always have perpetual problems with weeds and algae that always grow in shallow water 5ft and less deep. Weeds and algae are rarely problems in deeper water. Plant control will always be an ongoing increasing expense due to pond aging, annual nutrient and organics accumulation and sedimentation. Tree leaves are a big contributor to more shallow water and muck accumulation For long term planning strongly consider rebuilding the pond. If money is limiting then consider rebuilding the pond deeper but smaller. A rebuilt deeper pond will be lower cost to maintain, fewer chemicalizations, less work - less maintenance, less pond stress, and more pond enjoyment. Rebuild it right and it will be an improved long term asset not a liability that rapidly continues to fill in and create more weed algae problems. Filling in and aging is a natural part of the life of a pond. The speed or rate of degradation is the big variable based on pond location and basin morphometry (basin shape).

To address your aeration concern, I think for a 1.3ac pond you should first determine the natural depth of water mixing in this pond. In a 1 ac pond with good wind exposure the water can naturally mix down to 6-8ft sometimes 9ft. Water clarity and pond overall productivity also play roles in how deep dissolved oxygen is produced in the pond. High turbidity of 12" - 16" results in DO just produced in the upper 3-4ft whereas water clarity of 3 ft to 4 ft allows plants to make DO 6 to 10ft deep. It all depends on clarity. Know your oxygen and temperature water column profiles. If your pond does not have DO on the bottom then aeration is a big benefit to bottom sediment health with oxygenated conditions. So before spending quite a bit of money on aeration know the depth of natural water mixing in the pond and how deep the DO exists during mid summer. Clear water ponds with water less than 9-10 ft often do no need to be extensively aerated. Use aeration just during low DO periods or midsummer.