Generally, your last couple reps should be very hard to get up, this is a good thing as you are using the appropriate weight for your given rep range. So, in other words, you are doing the right thing.
As with the shaking, you will find the more you train, the less shaking will occur in these lifts even when you get near failure, especially the squat. You're just reaching your threshold. Keep doing what you're doing.
Remember, say you can do 225 lbs for 5 reps on your first set, you might need to lower that weight accordingly in your later sets to stay in your rep range. It takes some experimentation of course. This is where keeping a workout log is handy, because you can always look back at your last workout to see what you were doing and where you need to improve. Good luck.