All right, I had a chance to go back through the brewing notes from many years ago... Assuming the Coopers Lager Extract can is the same I used back then...
The can is pre-hopped, so no bitterness hop addition is needed.
The can is 1.7Kg or 3.75Lb.
To make 5 gallons (18.9L) I add about 3Lb or 1.36Kg of Dried Malt Extract.
If you are making around 3 to 4 gallons then the single can with 1Lb Dried Malt Extract you should be OK. If you are going up tp 5 gallons, I would add another 1 to 2 Lb Dried Malt extract.
Essentially, if you do not have enough Malt then the beer is going to be thin and watery.
Also, steeping the grains below 75C is a very good practice (as you know from Palmer's Book)
I encourage you to try your recipe, and if after you taste it (and it will taste good by the way!!!) you think Hmm too hoppy, or not Hoppy enough, or I wish this had just a little more body... you now have some tools to make those changes in your next back.
In my opinion, drinking the beer is only half the fun! The other half is dissecting what I would or would not change about every beer I have made, and change the recipe or brewing process to make that flavor change happen.
It is really a lot of fun!!! Good luck!