Frame size confusion

[SkipdiverJohn]

19.5" frame should be ample for someone at 5"10.

Could you put the saddle at correct height and take a picture sideways on with you on it.

That depends how long your legs are. how high you want the bars relative to the saddle, and whether the top tube slopes or is horizontal. It's quite clear the OP does not favour the arse up head down riding stance any more than I do. Long legs combined with comfort riding positions require frames that are tall, at least at the front end.
The most important dimension is actually the distance between the centre of the front axle and the top of the headset, as it cuts through all the variability of tyre to fork crown clearance and head tube lengths that result.
I'm an inch and a half taller than the OP and on a horizontal top tube frame, I want it to be 23" ideally. These old Raleighs were set up for an inside leg of about 33 1/2".

The top one is a 23" welded horizontal TT frame, the bottom lugged one is "only" a 21" sloper TT but has a 7 1/2" tall head tube like the lugged 23" version.

 

[sasquath]

Tried the ring spanner technique. It bent the spanner!

Get steel spanners, plasticine ones you own are good for bin.

 

[DCBassman]

Just needs a slightly taller closer stem, and I think you'll be right, or at least in the ball-park.
QRs: ok, the rear is good, but I think you'll destroy the front getting it off.

 

[mikey567]

Just needs a slightly taller closer stem, and I think you'll be right, or at least in the ball-park.

That's what I am thinking. The current stem allows me a 1 inch increase, and after also experimenting with the seat height and the ride position is slightly better. Especially if I wear gloves to stop my hands getting sore.
In the longer term, I probably need a longer stem. Maybe just an extra inch would fix it.

QRs: ok, the rear is good, but I think you'll destroy the front getting it off.

Managed to release the front QR, using a massive Chrome Vanadium screwdriver wrapped in a towel. I lubricated the area, but was then unable to close the QR. I rotated it half a turn anti-clockwise and then was able to finally get it closed.