Missing a couple things. One they need more prominant boney ridges on their forehead, jawline and cheekbones. Also they usually have a very slight shade of yellow-green gradiated up to their foreheads. I have taken cues from the Nemesis movie and designed mine this way.. he even has a scar with the inner part shaded green to give him that green blooded look.
I like your tutorials, but this one I think needs a bit more seasoning.
Show me what you mean if you can, but what you're saying doesn't seem to translate well in the creator. Hence I had to compromise on more than one occasion. The bony ridges you're looking for will make characters appear far too gaunt.
I think I've found dang near the perfect forehead bit, "Kesat." Went back looking for the forehead detail they use on the in-game Romulans (easily seen, just hail an enemy sensor contact in the Alpha Centauri sector unfortunately it isn't in the creator) and stumbled on this.
After examining some Romulans up close in-game, they seem to be a darker shade of green that I don't like. I think my selection is a happy medium. Some of them have bony-er faces, but that's a little tough to reproduce in the creator.
A note on the Nero tats...in normal Romulan society, one who is mourning will put on henna like marks to mark their grief for their period of mourning. Nero and his crew made their marks permanent to mark their grief for their race...so, just a point of reference for your backstories
From what I can tell of the Romulans I've seen in-game, the ridges seem to be a trait that is not universal; that is, there is one or more races of the species Romulan that have them, and one or more that don't.
Which would make sense, given that they were originally Vulcan.
As a side note, humanity is actually very very genetically homogenous; we have less genetic variation across our entire species than an average tribe of chimps. Despite that homogeneity, look at how different humans can be; it's not hard to imagine an older, less homogenous race covering several planets having more varied appearance.