As for concerns about the corner, I had already decided to TIG the root pass with my SyncroWave 250Dx. As stated before the inner 1/8" of the corner of the weld will be machined out afterwards. I think @adama mentioned shrinkage but I have a solid plan for fixturing. Im also as is standard practice with all the work I do like this going to send it out to get normalized.
No do not fixture heavy sections that hard, use preheat to control shrinkage, but if you manage to fixture 1" thick materials dead solid and take no other measures the welds will just crack as it cools. Molten metal shrinks as it solidifies, it continues to shrink as it then cools to ambient, its a basic fact of the physics of welding, as a welder its all about managing that, not fighting it! Post weld normalization is great practice, but it won't remove any cracks you have that are there from a over constrained weldment thats been carried out badly. IE it fixes and improves things, but it won't reverse any errors or defects. On heavier stuff like this it also pays to use the lowest grade filler tensile wise you can get away with, again it just reduces cracking risks through shrinkage as it yeilds and stretches as it cools. Also eliminates issues like hydrogen cracking too. IMHO a really common NOOB engineer-welder mistake is over specifying welding materials to try and gain strength when in reality there just increasing the likely hood of joint failure.
For etch, if you warm a section std vinger or any of the acid based toilet cleaners will work in a push, not ideal, but will make it really clear as to what is going on.
Globular is splatter heaven, gotta go up above there or stay bellow.
In practice how ever you do that root that corner may well still have a lot longer life if its not there, very few parts fail do to outright lack of strength, most fail in fatigue do to stress rises like that kinda corner weld. Structures have a nasty habit of focusing stresses into corners, by not haveing any material in that focal point the part ends up far far stronger, its counter intuative till you run it through FEA type software and see how by removeing that focal point of material, even 1/2" away the sresses are then down so much lower and into numbers that won't cause a material failure. Its kinda all down to the reasons cracks proper-gate, its not so much the way the crack weakens the material, its all down to how the crack focuses the stress at the very end of it till it proper-gates.