what are the steps to kick off the dismiss procedure except for
sending him an email of notice?
In addition to sending him an email, you should also notify him via USPS Certified Mail with Return Receipt. That will make it harder for him to deny his awareness of your decision to fire him (keep in mind that he might otherwise try to send you more bills).
You also need to file in court a motion for substitution of counsel (serving a copy thereof to any other parties). The motion's label is not as important as the assertions you make in it. In that motion you will indicate that you wish to proceed in pro per, or identify the attorney who henceforth will represent you (I think the new attorney will have to file in court a notice of appearance, but I am not sure).
Although you are not expected to explain in your motion the reasons for firing the lawyer, I would encourage you to state them, as these might be relevant if your matter ends up in an appellate court.
how to draft such a motion, what's format?
I strongly encourage you to get acquainted with the court rules (aka rules of procedure) of the jurisdiction where your matter is being litigated. There are significant overlaps of procedural law among jurisdictions, but there might also be some noteworthy differences.
Roughly speaking, a motion consists of:
- motion header;
- the facts on which your motion is premised;
- the relief you expect from that motion;
- a brief, where the party develops his legal arguments and presents laws favoring his position.
Given the nature of this motion in particular, you might not have to cite laws except the procedural provision(s) (if any) addressing substitution of counsel. More generally, http://www.leagle.com/leaglesearch?exact=immigration+court is a great resource where you can find case law with which to support your arguments.
I have never litigated in immigration court, but in the latter portion of this page (see section Trial Court) you will see various motions filed by me (and others by the defendant) in one of my cases in state court.
Although I promote litigation in pro per, the whole process (starting with the learning curve) is very challenging. On the bright side, you are about to save thousands of dollars and gain much more control over your case than through a lawyer.
And once your matter runs its course, don't forget to report the lawyer with the corresponding agency in charge of disciplining malpracticing attorneys (for instance, in Michigan it would be the Attorney Grievance Commission). We pro se litigants have to endure so much prejudice, whereas situations like yours show that the legal "profession" leaves much to be desired.