masonry without bw won't get you sh from a certain lvl. on; you'll just miss it even with bonus from connected stone. Guess that's what TMIT is tryin' to say.
regarding monument - if needed, work it till 2, whip it at 2(there's no point in building a gran. and then switch 1 turn before pop. 2 to monument and whip it a 2 - it just adds unnecessary microing... either via overflow or via turns spent on gran at pop. 1, you'll still get same hammers in it).
I try to get it asap when it's the case(if really needed for a key resource which is in 2nd ring, I'll even chop it), otherwise, pass it till some religion spreads unless everything is in 2nd ring. Another prob. I have with sh is that those don't double the cultural output in 1k years and when your city generates 3 culture(monument + lib), 1 more is 33% increase and can result in controlling another tile or 2.
regarding workers in new cities - if city at size 2 and I have a spare worker - chop a forest, whip and get another(that goes for city 2-3 when capitol does some wonder or crap and I can't afford building them in capitol or when cap. ain't too great and I run two scientists so the output is poor).
on marathon I was using groups of 3 workers. Since everything is x3(all actions regarding workers), all you'll waste is transit time. And frankly... you have time on marathon
on normal I group them only if 2-3 cities are waiting for that improvement - say, a dye tile - city owning it waits to work it, city 2-3 are already in unhappiness awaiting for the new resource. Otherwise, as tedious as it is, I keep them ungrouped. Other exceptions being chain irrigation and groups of 2 when needing a railroad to front line asap and I just got the tech.