Let me start by referencing this photo.
So it sounds like when you say you had a gap it is really two rounded parts coming together. More this than what I was thinking in that the square tubing wasn't lined up with the shoe as you call it on the SSQA or FEL. I was thinking this was the problem because it is possible to tweak things on the FEL where the two dump/curl cylinders are a little out of sync so the shoe on the FEL side isn't quite square on the left vs right side. I have a buddy that has a Kubota (with SSQA) and his is tweaked a bit so it makes it hard to get attachments on.
Of course everything has been painted and the photo isn't close enough with any of the welds to see if shielding gas is an issue but the weld a lot of times will look like it has air bubbles in it. There will be what looks like pinholes. We can't see this since it was painted and the photo isn't good enough. Another possible cause is too much stick out. Meaning the wire was out too far or your nozzle wasn't close enough to your work. A rule of thumb is no more than 1/2 of wire from the nozzle. I often shoot for closer to 1/4". A solution is to increase flow (or pressure), weld inside or switch to a flux core wire. I am not saying this was an issue but it is pretty common to new people to welding. I should note that the first weld photo I posted before was with flux core not solid with shielding gas like I use now. I forgot when I did that, I had just gotten the welder, hence my first weld, and I was playing around with the flux core wire that came with it. That is common to ship with flux core so you can get started right away as they don't ship them with a tank of shielding gas.
Lets start with the red circle. It sounds like the square tube which had a round corner and the FEL Shoe were being welded together. This isn't necessarily a bad thing. Many times a strategy for welding two thick pieces of steel together is to have a V notch. What it looks like you were doing was jumping from one side to the other. The proper technique is to Run your first bead down the bottom of the V. Then stack more beads up to fill in the gap. This is a multi pass weld. You still want to make sure things were aligned like I mentioned with the example of the the Kubota where the FEL was tweaked. The square tubing should be flat against the FEL shoe as well as flat against the SSQA Shoe. This shows welding in a corner but in a way it was kind of what you were doing.
What you don't want to do is bounce back and forth crossing the gap which is what I see here.
For the blue circle it is more of the same. I am trying to tell what we are seeing here but it looks like you have your bucket on your SSQA. The steel on the left edge of the blue circle is the SSQA that you welded to your bucket so you can remove that to get better access at those welds. It isn't like you were trying to work around that steel on the left.
What I am seeing here is good signs of no penetration. See how the weld just is sitting on the steel? It looks like a bead of caulk that was just squirted on the steel and just sitting on top. It should be burned in more. This is often a sign of not enough amps or possibly your grounding clamp wasn't attached very well. Some of this can come from learning the sound. A poor ground can sound more like popping where when things are running well it will sound more like sizzling bacon. You want bacon not popcorn.
A fix for a better ground is making sure you are clamping on clean steel. Also a lot of people will take a bunch of scrap copper wire, twist it up and place it between the clamp and the steel to just get better surface area for the ground clamp
Of course the fix for the wrong settings are to use the right settings which can also be the problem is to use he right settings. Consult the owner's manual or like I said, my welder has a chart inside the door where you load the wire.
A lack of penetration is a clear issue, you can see what can happen in this photo when someone started stacking welds. The temp changes caused stress which popped the bead loose.
The black circles I assume are where you attached the bucket to the SSQA plate to make it compatible with your new QA. You just have a small bead on the top and bottom. I assume maybe you are thinking with JDQA it only has those two points and you should be good. Weld up that entire gap. Wire is cheap. It is more practice.
As
@ttazzman mentioned which was a good point, weld flat when you can. You should have been able to weld that square tube to the SSQA on a workbench. Those were your easy welds. The welds on the FEL are going to be harder and try and go bottom up. But practice this as well.
While nothing will replace a good community education or some other program where you can learn welding hands on with an instructor, if you don't have access to this, youtube might be another good source. There are lots of good videos on what good welding is like and bad welding. Things to look for, sounds you should hear and overall techniques. While I covered a lot here, it isn't nearly everything. Just some of the more common things and what I could see in the one photo as well as trying to possibly correct some of these issues. Since it was painted it makes it a little harder to tell for sure. Rather than just saying you suck, I am trying to point out how to do it better. That said, this is more of a critical bit of welding so it might be good to consider a pro or at a minimum practice more and go back and readdress these issues. The good news is you have a grinder.