Add this to your model after instantiating auth,crud and mail.:

def store_in_db(db,settings,tablename):            
    validtypes = dict(string=type('t'),integer=type(3),double=type(3.0),boolean=type(True))    
    def get_dbtype(f,d):
        for k,v in validtypes.items():
            if v==type(d[f]): return k
        return 'string'    
    fields = [db.Field(f,get_dbtype(f,settings)) for f in settings if type(settings[f]) in validtypes.values()]
    db.define_table(tablename,*fields)

    if db(db[tablename].id>0).count() == 0:
        vals = dict([(k.name,settings[k.name]) for k in fields])
        db[tablename].insert(**vals)

    for k,v in db().select(db[tablename].ALL).first().items(): settings[k] = v

Now tell it to save your crud settings in the database:

store_in_db(db,crud.settings,'crud_settings')