Yes, the bottom carabiner can just be clipped into the two rings...but that's a nasty harness, I can't think you'd be comfortable for any length of time in that.
Would you consider any saddle with padded independent leg loops an improvement over the saddle pictured? It's a Weaver wideback saddle that comes with the kit I ordered from WesSpur. The problem I might run into is whether a particular saddle will fit me. About a 46" waist, many of them don't seem to come in that size.
Yes, any thin loops or webbing is going to cut into you before very long sitting in the harness, especially if I extrapolate your weight as being proportional to your waist size, thin loops will make you miserable eventually..
Looks like tape to form a 'trap'.
6'3" - 6'4", two hundred and mumble mumble pounds...