There is no set fee for personal injury cases.
In your case, presumably, there was an initial consultation with solicitor. He would be entitled to be paid for that. He then had to complete the IB form, which would have taken perhaps 30 mins. he is entitled to be paid for that. he would have requested medical reports and he is entitled to his fee for the time spent on that, as well as the fees spent on the report(s).
The figure you quote seems excessive in the extreme. He seems to be basing it on what you would have recovered had the case gone all the way to the High Court.
After the initial consultation, he should have sent you an estimate of fees, or if that was not possible, his schedule of fees, such as the hourly rate etc.
I don't know where you live, but if it is in a small town, you need to move to your nearest big town/city to get advice from another solicitor.
There is no necessity in fact for you to have a solicitor involved at all in an IB case. It is a simple case of filling out a form, sending it off with €45 and a medical report and then going for whatever medical examinations the IB ask you to go to. If you feel that you are not improving, you can send them a subsequent report and can always wait until the award is made before going to a Solicitor to see if it there or thereabouts.
I forgot, IB have now issued an Authorisation, meaning you are free to pursue in Court, so you WILL need a solicitor. Follow suggestion in para 5 above.