It always amazes me how many times the same issues are discussed here.
1: Indeed. Use bacteriostatic water, NOT the diluent included with the package, it does not have any bacteriostatic properties.
2: There is no need for larger vials. Mix half the amount of diluent with the HCG at 0.5ml/1000iu, and inject half the fluid volume for the same dose compared to 1ml/1000iu.