Toyota Repair: 3 questions, any help would be appreciated

Question
Lexus is300 2001 . Recent maintenance- new radiator. New tires, new o2 sensor after replacing the
CEL code -P0420   Catalyst System Efficiency Below Threshold came on

When I'm driving especially on the interstate something splashes on my windshield that isn't water bc it smears when I turn wiper on.
My second question- I have a rough idle now that vibrates the car sometimes when I'm in gear and while in park when engine is warming up. when I put my car in reverse it idles rough and the when  I back up it feels like the tires are braking bc it hesitates like it keeps snagging
My third question - I have a squeak when I turn (like into a parking space) and when I am sitting still in drive if I turn the wheel I hear the squeak from the front right wheel area.

Answer
Hello, it sounds like the liquid splashing on you windshield is engine coolant, I know that a new radiator was put in, if the engine overheated before there is a chance that it now has a leaking headgasket, this creates more pressure in the cooling system and can force coolant out into the overflow bottle, when this happens the coolant can be forced out of the coolant bottle at the top, the rough idle and loss of power also points to a possible head gasket issue, the squeeking is most likely caused by the rubber bushing where the steering column exits through the firewall, it can be lubricated using a silicon spray. What I would recommend you do is to have a repair shop test for a leaking headgasket, this can be done using a simple chemical test that detects hydrocarbon emissions in the cooling system.