I don't understand your description of the throttle problem. The engine has a governor, so the control on the handlebar is a speed control: it sets the governed engine speed, and the throttle itself is opened and closed by the governor to keep the engine constantly at the speed you set, regardless of load. You may be saying that the speed control cable doesn't work - moving the lever doesn't move the governor lever at the engine end. If that happens one end of your cable is either loose, or has kinked, so moving the upper end doesn't move the bottom end. If that has happened you have to see exactly what has gone wrong, and tell us or post a picture. It is probably extremely easy to fix - just a screwdriver adjustment of the cable position and/or lubricating the cable.
It sounds as if your mower had a couple of trivial problems, which sometimes happens with new mowers and the dealer normally fixes them under warranty. Not having a warranty, if you follow Joe's advice above you will probably overcome your starting problem, and proper set-up of your speed control cable should fix that even more easily. Don't decide that the mower is garbage - these are things that are fairly routine for a lot of machines when they are brand new, but once it settles down it will probably be trouble-free for years.
