No feats - Practised Spellcaster won't help you, since it's capped at hit dice, not ECL.
One thing that might help you (if you can convince your DM) is the LA Buyback variant rule from Unearthed Arcana.
Regarding the difference between ECL and CR - there are some abilities that are significantly useful to a PC, but which do not significantly increase the challenge of an NPC.
Let's take three examples.
We have an NPC with two scrolls of fireball. We have an NPC who can use fireball as a spell-like ability twice per day. And we have an NPC who can use fireball at will.
Essentially, for a monster who will be encountered and fought by the PCs, these are all of similar benefit to the challenge it represents. A fight might last five rounds, and it's unlikely that the at-will fireballer will be letting off a fireball every round. It's not unreasonable to assume that all three of these NPCs will get off a couple of fireballs before the fight is over.
Now let's take three more examples.
We have an PC with two scrolls of fireball. We have an PC who can use fireball as a spell-like ability twice per day. And we have an PC who can use fireball at will.
The first PC could use the scrolls once, but then they're gone.
The second PC could use two fireballs in one combat each day, but in any other combats that occur that day, he won't have any left.
The third PC can use two (or more) fireballs, in every combat that occurs, even if there are fifteen encounters in one day.
So while the three abilities represent roughly the same increase in the challenge an NPC combat encounter represents (thus in theory giving about the same increase in the NPC's CR), they are of wildly varying usefulness to a PC (and thus the LA they represent would be wildly different also).
-Hyp.