Very useful information. I tried to do this in a different fashion, but my project failed due to starvation and annoying hauling tasks.
Can you confirm whether or not the lover/marriage tags are mutually exclusive? That is, if a dwarf has a marriage tag enabled, will they still first form a romance or do they need the romance flag enabled as well?
All my testing was with ONLY the heterosexual marriage tag set, all other flags set to false. Lover/Marriage is NOT mutually exclusive, but part of the progression:
Friends > Lovers > Marriage
My suspicion is that any dwarf with a romance tag will tend to get stopped at the "lover" phase, whether this overrides the marriage flag has yet to be seen (that will be my next test).
Another note: Anyone who is a planter with large fields can almost be written off entirely as part of a viable pairing. They just spend too much time working. For the context of this challenge, I'd say to juggle the planting responsibilities onto a married dwarf once you have one to free up the planter for love.
Also of note: Once your dwarves start having babies, they'll be squirting one out about once a year like clockwork. At year 7, this fort is 7 dwarves, 9 children, and 3 babies.
Addendum: Personality appears to play more than a passing role in whether relationships are possible. I had a dwarf with 3 of the "no-fly" personality traits, and they barely made any friends and never really progressed past being a friend to those he did get close to. So, if you're looking to play match-maker, keep an eye on those personality traits. Anything that suggests social ineptitude or a negative personality seems to really kill any chance they have at forming any meaningful relations with other dwarves.
On the plus side, these are the ones to keep track of. Once the spiral starts, these nega-dwarves are the ones you want to burrow in safety and wall up until things either calm down, or the last tantruming dwarf is dead. If they've been kept relatively busy, they won't have any friends to mourn.