I am 250lbs and felt that the thing would move a bit from side to side at speed but it would take a very deliberate throwing of weight to tip it over - the base is very heavy. The biggest issue is the tendency for one wheel to leave the track. See other reviews but this seems to be a combination of weight (230 lbs+) of user, occasional loosened bolts, and ungreased rails. If you are under 230, you may never have an issue but I was frustrated with it given that it is advertised as suitable for much heavier weights.
If this is an issue with sound or clicking noises when in use, I purchased the rubber exercise mat recommended. This helps both with sound issues and the soft material keeps the center of gravity changes to a minimum. I have not needed a lubricant that is suggested. Sorry.
The real warranty is the lessor of the two. However once I showed amazon the error on their site, they emailed me a letter stating they would honor the better warranty. I'm not sure why they haven't updated their site.
You can't adjust the stride length. You can only adjust the stride incline (which may slightly increase stride length by perhaps 2 inches at max) and the resistance. Stride length is not a feature that elipticals have unless you can somehow find one with interchangeable fly-wheels. (hint...no such eliptical exists)