Yeah, forgot the sound.. Tire sounds to max, that's definitely the way to go. SFX, road noise, not so crucial. Lack of FFB, can't help there as i started with momo but when FFB disappears, i'm completely lost. So there's hope, i've seen people with 30€ wheel do amazing times. In some occasions, i believe that without force there's possibility to go even faster as it doesn't stop you doing extreme/unrealistic maneuvers.
But in the end, try getting a FFB wheel. I can recommend a good secondhand Momo Force (not one that has been in use for 5 years...), i'll post a modding guide with pictures the next time i need to do maintance on it (in 2 months time). Those mods are cheap (~10€) and with them the Momo is much better than anyone expects, something like G25 quality. It lacks finess with its simple cogwheels and that single motor is a little underpowered but it's enough to get the responses that the game produces.
The racingline can seem like it's correct, only way find out is to get a replay/hotlap from some experienced driver and comparing it to your own. The tutor needs to drive at 95% speed, not doing kamikaze qualify superpole stuff..What i found that even i thought my racingline was correct, the way Nick was turning showed me the error of my way. I turned a lot more and straightened the wheel much later. The reason was i took the initial turn too early. I got as far as apex with great speed, usually more than others and that thought me that i was going faster than others.. Not.. The car was understeering at the exit and my straight line speed suffered. Now it's opposite: way longer braking than others (comparing to public racing, not to the really good drivers in closed leagues where i usually drive..), constant apex and way faster exit. Most racers in public servers, which represents the lower end of scale in skill, brake way too late and you can pretty much pass them before the corner is over by keeping the speed more consistent...
If in RWD the rear snaps off when downshifting, you can delay that without consecuences. Just "miss" one shift, ie if you normally do it [ brake,6,5,4,3,2 ] try do it: [ brake,nothing,6,5,4,3 and shift to 2nd just before you need to accelerate. Quick tap before the last downshift can help to match the engine RPM to drivetrain speed but i suggest that you do that part of later. I'm doing under 2 minutes in Monza but not much under.. It's slowly improving but those last two seconds take a looong looong time...I've driven with a wheel over a year, with pad from the GT2 era.