Only a few areas
with tidal gauges seem to be far enough away from plate boundaries for it not to be a possible factor, e.g., northern Europe, eastern North America, central Pacific islands.
Seems quite a bit easier to go
with the tidal gauge record; it has its complications, but at least you are starting with reasonably direct measurements of sea level.
Again, to justify applying another positive adjustment (this time, nearly doubling the trend from +1.7 mm / yr to +2.8 mm / yr), they relied on a comparison
with tidal gauge trends!
Despite the various problems
with the tidal gauge data, it is possible that the various estimates of global sea level trends of 1 - 2 or maybe 2 - 3 mm / year might coincidentally be correct.
Finally, as we discuss here, there are a number of problems
with the tidal gauge data, so even that estimate of a 1 foot rise every 100 - 300 years is probably an overestimate.
Not exact matches
Though examiniation of old
tidal gauges are good, many were painted wood and metal
with a life of between 7 - 15 years.
I realize that
tidal gauge measurements for assessing sea level rise has met
with some skepticism because of multiple measurement issues including tides, ground water pumping and subsidence, tectonic plate movement, glacial rebound, etc..
The 2014 White et al study finds that this is consistent
with global
tidal gauge measurements.
Furthermore, you complain about climate scientists not going «back and check the input data» when you yourself failed to do so
with regard to the
tidal gauges you were touting.
With respect to Church et al 2008, you're neglecting to mention (or perhaps didn't read enough of the paper to notice) is that, unlike you're «eyeballing» method, they actually adjusted
tidal gauges for changes in local land elevation before drawing any conclusions from unadjusted data.