Hi Ricardo,
1) You should change the -Xms to 512m ( ie you are allocating 512 Mbs for Xms ) . Rest all values should be fine. Its should look like this
-Dfile.encoding=UTF-8
-Xms512m
2) Both 32 and 64 bit versions are fine . Just make sure that you have installed the same version of HANA Studio ie 32 bit Studio for 32 JRE and like wise for 64 bit. ( Infact changing the JRE is easier 
)
BR
Rahul Jha