I would think that 1998 would be closer than 1993 for this tractor. From the factory, the chute was not bent as per your picture, although it is not uncommon to see these decks bent like that from running into trees, stumps, and other non movable objects. It originally had a guard in the opening that would help prevent this, but many took off the guard to help deisperse the clippings better.
Not sure which lever you are asking about? Is it up by the dash or on the rear end of the tractor? There is a parking brake handle down by your feet that is basically a handle that rides on a radius and overcenters to lock the parking brake. Some slop will develop on any linkage over time. I wouldn't think that there should be excess slop that couldn't be adjusted on a tractor of this vintage, although anything is possible. When you lift the seat, there is a bracket on top on the transmission that sits over two relief valves. When you press the lever down, it depressed the valves, allowing the hydrostat to be pushed much easier because the fluid is being bypassed. When you lift the lever the valves should come up and close off the bypass action. Sometimes they will stick or not come up all the way and you either won't get any action from the transmission or it will partially bypass causing you to not have full pressure resulting in decreased speed. Check them both out and make sure they are both open to the same heighth.
The 7100 series preceded your unit. The next series after the 7100 was the GTH series, followed by your Sovereign System 18 was introduced in 1997. Depending upon which tractor you have, there are several mfg ID numbers that can pertain to it.
1693410 - Sovereign, 18HP OHC Hydro and 48" Mower Deck
1693409 - Sovereign, 18HP OHC Hydro
1693408 - Sovereign, 18HP OHC Hydro w/PS and 48" Mower Deck
1693407 - Sovereign, 18HP OHC Hydro w/PS
1693146 - Sovereign, 18HP Hydro w/PS
1692946 - Sovereign, 18HP OHC Hydro and 48" Mower Deck
1692945 - Sovereign, 18HP OHC Hydro
1692944 - Sovereign, 18HP OHC Hydro w/PS and 48" Mower Deck
1692943 - Sovereign, 18HP OHC Hydro w/PS
1692896 - Sovereign, 18HP Hydro and 48" Mower Deck
1692895 - Sovereign, 18HP Hydro w/PS and 48" Mower Deck
1692889 - Sovereign, 75th Anniversary, 18HP OHCHydro
1692799 - Sovereign, 18HP Hydro w/PS and 48" Mower Deck
1692798 - Sovereign, 18HP Hydro w/PS
1692797 - Sovereign, 18HP Hydro and 48" Mower Deck
1692796 - Sovereign, 18HP Hydro
1692450 - Sovereign, 18HP
1692449 - Sovereign, 18HP and 48" Mower Deck
1692146 - Sovereign 18HP, Hydro and 42" Mower Deck
1692145 - Sovereign 18HP, Hydro and 48" Mower Deck
1692143 - Sovereign 18HP, Hydro
All of these are pretty much identical as far as the main features and any of the manuals will cover about 98% of all of them. They all used the Sunstrand Hydrostat and the settings for them are all the same. The first ones released had an oiling problem in the Kohler engines and many grenaded in the first 100 hours. These were replaced with a redesigned engine and later ones had other power plant options also.
Hope this is of some help to you. Any of the above mfg. ID numbers should get you a manual that will give you the information to check and adjust the transmission.
