Welcome Jazman. Only you can answer if surgery is the right choice for you, but it sounds like you haven't really evaluated all of the options that are out there for ITP treatment. Lots of old school hematologists push patients into splenectomies without offering all of the options available. Good hematologists don't use splenectomy as a treatment option after trying a lot more things than just Rituxan or IVIg. Rituxan is a good treatment for lots of people, and it sounds like it worked well for you the first time around and gave you a year of remission. Others can talk about allergic reactions and how they manage those... I think someone is managing an allergic reaction of hives by doing a very slow infusion with allergy medications. You can search and read about that in another thread.
Regarding IVIg, this is not really a "treatment" for ITP. Some people get an increased count from IVIg, but even those that do usually crash back down a few days to a few weeks after the infusion. It is not a maintenance treatment, and people use it as a rescue treatment when they need to get counts up for other reasons (upcoming procedures, stopping bleeding, other rescue measures).
The main modern ITP treatments are Promacta (Eltrombopag) and NPlate. It doesn't sound like your hematologist has even offered one of those. Some people can also get responses with steroids (how is your steroid response?).
I had a splenectomy done more than 30 years ago because we didn't have many ITP treatments available when I was a child. It didn't work for me and I have to manage my ITP as well as potential complications of splenectomy (need for Pneumonia immunizations, having to be ULTRA careful with any fevers because sepsis is a big risk, higher risk of thrombosis and clotting events, etc.).
Some people do okay with a splenectomy and can achieve a remission for varying amounts of time (months, sometimes years). For others it doesn't work at all and you just end up removing a healthy organ. There is never an urgent rush for a splenectomy, so don't let any doctor try to push you into it. You should take your time and read and be convinced that you would rather do a surgery than try some of the many other treatments available. If your doctor is pushing you that it is urgent, then you need a new doctor. By the fact that your doctor is doing this after only trying Rituxan, it sounds to me like he/she doesn't have a lot of experience with ITP and is not up to date on current treatment methods.
I hope you can reschedule/cancel the surgery until you can make a more informed decision!