Block nonce predictable Is the block nonce predictable in any way? It seems to be a proof of work on his own just like the block hash, but may a miner force a mined block to have a specific nonce? (if his hashrate allows him to)
No it is not predictable. If it was that would break how block discovery works.

To explain in very broad terms: a nonce is simply an incrementing number. It is combined with a random set of as yet unconfirmed transactions and passed through a simple hashing algorithm, which turns it into a long number called a hash.

It's this answer (the hash) that has to match the test : it needs to begin with a certain number of zeros for the block of transactions to have been considered "discovered", and hence confirmed. 

If it does not match this test, the nonce is incremented by and the process begins again.

It is the fact that the number and content of the transactions combined with the nonce supplies the essential unpredictability of the process, meaning that ultimately nobody can say which miner will find the block.

As this is quite a heavy computing task (to continuously try new nonces and transactions until you find the block) the nonce also serves another purpose : to help other bitcoin nodes take a shortcut to check if the block you claim you discovered is correct. They simply need to take all the transactions in the block (you have to tell them which ones) and use the nonce to arrive at the correct Hash with the right number of zeros. This by contrast is a very light computing task.