Raevlav, Masterrazor, sorry but you should live with this 32 bit "official" solution. I know it might cause some memory limitations, but I have no idea how to use a recent Java 64 bit version in your cases.
The only solution that might still work for a while is to install a 64 bit version of Sweet Home 3D that works for you, backup the [font=courier new]jre8[/font] folder found in the installation folder, install the 64 bit version of Sweet Home 3D 6.1.2 and replace its [font=courier new]jre8[/font] folder by the backup you kept.