Don't taper on your own....check with your doctor first. Tapering from that level will probably take some time and that assumes you have no problems on the way down.
My initial tapers were about 10mg per MONTH from 60 to 40mg, 5mg per month to 20mb, 2.5mg per 2 months to 10mg and then 1mg per 2 months to 5 where I am currently.
Tapering too fast can cause all sorts of problems, some of them serious. There is a difference of opinion about how fast to taper but SLOWLY is always best unless there are some other urgent reasons to taper more rapidly. Just wanting to get off is not an urgent reason. You can seriously disrupt your body and immune system by tapering too rapidly.
Hope your ivig treatments work for you and you can eventually taper off prednisone. The impact of ivig does wear off and if you have no other controlling meds when you taper prednisone there will be nothing controlling your immune system and preventing future flares.
Bill