As you are single player, you have to adapt to your needs. I don't see anything wrong with it completely. I know you lack in the total items department, so eventually you find items or gamble for rares that will have leech. As you grow, you may find you didn't need to use those Amn's, but you can remove them with the cube later (if you find a Hel rune).
It's pretty tough to find awesome unique weapon as it is, especially in SP. Making high rune word weapons is near impossible. So I think socketing those weapons is a fine move. Later you might want to add a jewel or rune for damage.
There is a problem with the runeword thing. Only 1 socket. If you can add sockets to uniques that would help but I don't think you can. I think I might actually have a Hel rune now.... But at least I did something good. Even though I did I have the char backed up before I did the sockets so I can go back at any time. It's just 8% leech is not enough in Hell... D: Damn you non leechables!!!!
You also can't make runewords in uniques, only "white" items. But i think 2 Amns was a good idea until you can get the Life leech from elsewhere and as mentioned above a Hel rune (& tp scroll) will remove the Amns if you ever want to change the socket.
I agree with the others, Amn is fine. the nature of sockets is to adapt as you need. if your short in life leech (as can happen...i was hurting for ages on my first HC toon till i got a cathans ring in a nm drop), you adapt to what you need.
There is a cube recipe for "un"-socketing an item. It involves a Hel run and a few other minor items. not cheap, but hel runes start dropping in NM (i have 2 so far from random drops). keep in midn that it destroys whatever you put in there (bye bye amn rune), but its a viable option once you get higher runes and better socketing stujf available.
Also, Amn in a lightsabre isnt going to do you a whole lot of good. The majority of Lightsabre's damage is elemental, the physical part is very small - phase blades are notoriously weak in physical damage, their strength lies in speed. You might be better off sticking Shaels in them to maximize their speed, and then crafting a Blood ring (or Blood craft for any slot you can afford to change, maybe boots) for life leech.