Schwalbe make 1.8 to 2.1 in their tires. (Nobby nic for example)
Many reports Schwalbe measure up small as well.
As for the splashbacks, they have measured them at pretty much 1.8" including tread, to the person above measuring them quite a bit wider. Might depend on your setup or probably just the batch?
the seemed wide in my Manitou SX/XT V's (i.e i had to thump the front wheel in)
I just measured them with some digital calipers a tad under 2.2" across the tread and pretty much 2.0" across the carcass.
On a fully rigid they are bliss! (as well as being, light, cheap, grippy [all relatively!] and 95% look like a skinwall) Yeah my Nobby Nics are grippier per se but they are twice the price. certainly for retrobiking in all but the gloopiest of mud they are a fine tyre! To the OP try some 1.8's today!
I'd be very interested in the seatpost reflector if you decide to split.