I have just done this myself last weekend, and i used pattern parts. Pattern parts are an arse as they are never quite right, mine did not have the hole and threaded rivnut for my traction control so i had to improvise.
I know its a bit too late to say this now but the pinch bolt is a Torx head so the chances or rounding this fucker off are high, so what i always do is break the rust by undoing the nut on the other end first, then put the nut back on till the thead is level with the top of the nut and hammer it out, no need to touch the Torx head then.
What i learned when putting it back together again is that the right tools help, you will need to get an 18mm spanner on the end of the front bolt when you come to tourqe it up, think carefully where you put the spanner otherwise you will not be able to remove it again once you have tourqed up the bolt. I copper greased the inside of the front subframe so the arm can be manipulated better, put the front bolt in first and then a good pry bar can help you guide the rear of the arm into place, dont forget to fit the cam washer to the rear furthest nut, you have to angle tighten the bolts too after torquing them to around 115nm, the toruqe values are important as is the tightening procedure, dont try and do this without a torque wrench. Patience is the key. I had a disaster when i did the passenger side, i did not check i had located the ball joint into the hub so when i moved the car forward it slipped out the supension shot forward and ripped the inner driveshaft to bits lol
Hot water wont do a thing, dont worry about the stiffness of the bushes, i fittred polybushes to mine before i fitted them and trust me there is no give in these at all.
Try putting the bottom ball joint back in the knuckle as this may pull the rear of the control arm down enough to locate the bolts.