Hi Pisces,
I think it's perfectly alright to wear your ROM dress for the tea ceremony. Me planning to do that too...if not the dress quite wasted. Wore only once at the ROM. As for the EG, have you been to those "clearance" sale by bridal boutiques, where they sell off their EGs at a huge discount. Or alternatively, how about Celia Loe or something at Takashimaya?
As for Tam,I think I read somewhere that for traditional reason or something, suppose to change the gown when you go back to parents' house to symbolise that you have married out or something like that. Sorry..don't know the full details. You may want to check on that.