Hello so update and new info on my pond. My pond is roughly 1/2 arces. My goal is to have fun catchable LMB that range from 1-5 pounds. My pond is located in in NE PA and is spring fed from underneath and a stream that comes the mountains. All around the inside of the pond is weed line that is always full of the smaller BG. Larger BG's are pretty hard to come by but there is countless amounts of fry in the weeds. Next our not so helpful neighbor put in 2-5 goldfish or koi. What should I do with these?
Next my bass right now are at a decent sizes with the biggest one we caught being almost 4 lbs. These were bucket stocked a long time ago. I have keep the data of the LMB I caught. (L)ength (W)eight

L: 9.5 IN
W: .6 LBS

L: 11 IN
W: .63 Lbs

L: 14
W: 1.5

L: 16
W: 2.85

L:17
W:3.1

L:17
W: 3.25

L: 18
W: 3.75

L: 18.5
W: 3.5

L: 14
W: 1.3

L: 11.5
W: .8

L: 14
W: 1.5

L: 17.5
W: 3.30

L: 15
W: 1.6

L: 16.5
W: 3
None of my bass seem to be getting over 18 inches. I don't know if thats because the bass are stunted or they are just not getting that big. The pond has a healthy population of frogs. They are everywhere and I have seen the bass eat them.
Also I found one dead bass after winter. It was 9.5 inches and very discolored. Is this concerning? Overall, my goal is to add some SMB if possible there is decent structure and rock about 8 feet down. (Pond was dug deep by farmers to collect runoff in the early 1900's).

Summary.
Can I add SMB or YP?
Is the dead bass worrisome?
How do I deal with unwanted Goldfish/Koi?
Is my forage good? Can there be too much?
Are my bass stunted?
Thanks for reading if you have any questions feel free to ask!