I get nervous too whenever I make a cut that can't be undone. But hey, metal is easier than wood and way more forgiving. It may be overkill, but I would suggest that you add a re-enforcement plate on the inside of the frame across the weld on the top and bottom. I feel that is where the highest points of stress will be and the plates would be cheap insurance against cracks, etc..
I took a screen shot of your frame and drew on it to illustrate where I mean.
Glad to see updates from you, fair weather fox??? Just kidding of course, good to hear that you and the family are doing well. I look forward to seeing you again at a show & shine ( hopefully )
Keep at it, push it to the goal line, Steve
1946 Chev 1/2 ton - 6V/+ground/Bias-ply original - shake/Rattle and Roll! (SOLD) 1940 Chev 1/2 ton Franken/Restomod