I did lift up my 1987 V6 Cimarron at one of the places where the shop manual says to and one of the places where they say you can lift up front of car with a floor jack is the part of the frame between the front ends of the 2 FRONT SUSPENSION SUPPORT ASSEMBLYS, and using this part of the frame did lift car up but it smashed it in somewhat and caused the engine fan to jamb which I had to reposition so fan blades would turn freely. Would floor jack lifting under one of the FRONT SUSPENSION SUPPORT ASSEMBLYS be safe enough since the metal looks thick enough?
I've lifted my cars at the point you did, but I did it with a 2x4 laid up against it and the jack bed onto the 2x4. Works very well like that.
My 92 had a damaged one (where it had been jacked up without a board on it). I had it replaced. You can read about it and see the new one in place.
There is also a link where I bought mine, if they still have anymore.
No edit available, so I have to add here.
When I use the radiator support lower tie bar to jack one up, I remove the air deflector to get the 2x4 across it.