I might as well reply to this, even though it's pretty ancient by now.
Keep in mind I haven't logged in to RoM in months, so some things may have changed a little.
Examples are...I don't even really understand why Tier matters. Obviously higher tier stuff seems to be better statted and usually has high lvl req's...but I don't really understand the point. For example, your post talks primarily about tier 3 stuff...why not do all tier 4? Can you not put tier 4 stuff on lowbie gear? Or is it just a cost issue?
It is most definitely a cost issue. T4+ runes and mana stones on the AH are astronomically expensive. It's not worth the gold to put T4+ stats on lowbie gear, since you're going to end up replacing that gear eventually (I stat gear at level 20 or so and keep it for awhile. Then again, none of my chars are above level 29 since I stopped playing.)
I've seen some statted gear that maintained a 7th stat...(usually it's a garbage +3 stat or something)...how is that possible? I do know that some gear has multiple stats under a single "name" and therefore more than 6 is possible...but I've also seen 7 distinct green stats on items (6 named + 1 from..??).
You can buy driller tickets in the item shop that allow you to add additional rune slots to gear. That's how you can get above six green stats. If you see gear with yellow stats, those are generally two stats in a single rune.
Your example only talks about transmuting items with a single stat..what happens if you transmute a fusion stone with an item that has multiple stats...do you get the lowest 4 stats? (Assuming the fusion has the lowest 3 stats...it will *only* take the lowest one from the item???)
Your fusion stone will always result in the four lowest stats. That's why it's absolutely necessary that you get three fusion stones with identical stats. If you have scads of gold, you can get better stones with decent stats (or with only one or two stats instead of three), but for dirty statting, the cheapest route is get three stones with three low-level stats on them. You then fill up the remaining six stat slots on your gear with high-level stats.
I see weird stuff in chat sometimes about people "stripping" certain properties off of items, or set bonuses? Is there some way to get a stat off an item without destroying it?
That part I don't know. I don't think you can strip a stat off an item without destroying the item.
As far as set bonuses go, those are just stat bonuses you get for completing a gear set. Most (if not all) gear sets are made up of various quest reward items.