There's no easy way to say this...
Your seat isn't Tracker's problem. That seat has been exposed to the weather for a LONG time. My 1999 911 CDC which sat uncovered for about a year isn't in much worse shape. The good news is, the seat skins are fairly inexpensive and you can get them from Tracker parts.
That seat has been left out in the weather for an extended period of time and the UV rays have deteriorated the fabric to the point that the first time it got stepped on good, it ripped.
Seats should NEVER be stepped on (not that I manage to FOLLOW my own advice); they aren't made to withstand that.
You say the boat's only been to the lake a few times. Your profile doesn't say what year model it is, but if it's a 2003 or 2004 and you haven't left it outside uncovered, you got SCREWED by your dealer (assuming you bought it new). That is a $34k boat and you're not going to get anywhere near that out of it.
The spider cracks in the gelcoat are "normal" and not covered. I'm not suggesting that you should like it, just that your dealer told you right on it. You have one of the heaviest, widest 20' boats on the market. As such, it's going to have a fair amount of flex, which is what causes those spider cracks. Every brand of boat (but not every boat produced by any manufacturer) gets these spider cracks. MAYBE Ranger would cover them, but you've already paid for that kind of service when you bought a Ranger to begin with.
I have a 1999 Nitro 911CDC with a 225 Optimax that I'm trying to sell for $14k and haven't managed to get anyone to even come out and look at it. My boat IS used, has the war wounds to show it. With Nitro, your resale value isn't what one might hope, but I will tell you that you can't find another boat in that size, width, weight, storage, blah, blah, blah for $34k. Then again, there really isn't another boat on the market like the 911cdc.