1. Suspension parts do NOT cause vibrations, they can make them worse but they are not responsible for causing vibration, things that rotate cause vibration and BECAUSE you just had the tires replace I would recommend taking them back to recheck the balance and also to see if there is a tire problem, it’s not out of the realm of possibility that you threw one of the wheel balance weights that was just installed, in fact it happens all the time and some tires are better than others so if there is a problem with one of the tires it may show up right away, it could also be an issue with the installation.
2. Bad inner tie rods have nothing to do with a PS rack leak it’s just easier to replace the entire rack if you have a leak and loose inner tie rods because a new unit would come complete with new inner tie rods and new seals to prevent leaks. I’d have to see it for myself to make a real assessment on that however.
3. I’d say a good round number would be 15-20lbft on the pan bolts but as suggested check the service manual for the correct spec.