Keel question

[HitNruN]

During years I've learned a lot from this forum. Now I have new questions regarding the keel of my boat.
First question is about the keel not being level with the hull as if it was hit to rocks and got separated from the hull but this would cause some cracks, at least on the gelcoat but there are no cracks anywhere. Hull is in perfect condition. The keel to hull joint was laminated with fiberglass to keep it dry but it actually caused a bigger problem. Water found its way through the poorly made lamination and kept the keel wet even on the hard causing lots of rust. So, can the cause of keel not being level with the hull be a thick rust layer that tries to separate the keel from the hull?
The keel bolts seem fine from the inside the boat but very very rusty from the outside. Do I need to change them?
I know this is a millionth time someone asks how to clean the rust but a new opinion might make my day so I ask it anyway. I'm thinking of using an angle grinder sometimes with disks and sometimes with wire brush cup to clean the rust until bare metal. Sandblasting seems to be a very expensive deal even though it surely is the best option in my case. Do you suggest dropping the keel to get rid of the rust thoroughly or is it enough to clean from the outside and put 4 to 6 layers of epoxy barrier paint?
I also am planning to apply phosphoric acid before the barrier coat to eliminate rust returning fast.
Any idea is highly appreciated. Any pics if available would be wonderful if anyone has done this before and took pics during the process.

[HitNruN]

Pics of the keel...

[Lepke]

If this was my boat, and I planned to keep it, I would drop the keel so I could eliminate the rust. I would also pull a few keel bolts to check. I would sand blast. In the US, equipment can be rented.
I just started using a new rust remover that works very well. Archoil AR5100 Rust Remover found at archoil.com. It's water based, biodegradable and eats the rust and leaves no residue. It leaves a surface that looks like it was sand blasted. I used it on rusted tools by submerging them in a bucket. The solution doesn't hurt paint or metal coatings, just the rust. You would have to use rags or cotton wadding to hold the remover against the hull for several hours. It's supplied as a concentrate that dilutes 16:1. I did a pipe wrench I found in the bilge that was a lump of rust flakes. The solution cleaned the wrench and got into the adjustment nut and completely cleaned the threads overnight.
On the keel, it looks like the keel was completely covered with fiberglass that should have made a wt seal. Use epoxy resin not polyester. Polyester doesn't stick well to anything including itself.
Not completely eliminating the rust might be seen as hiding a problem.