Qadar - destined to do what Allah decrees?


When my convert friend learnt recently of the death of the son of someone I work with, he responded by suggesting I tell them that Allah decides how long we live: "There is nothing the parents could have done," he opined. "It might be a consolation for them to know that." Hmm.
I didn't tell them. I can't believe the thought that God had decided to take their two year-old from them would have provided much comfort.
And yet this concept of divine destiny (or qadar) is one of the six articles of faith in Islam (along with Belief in the Oneness of Allah, the Revealed Books, the Prophets of Islam, the Day of Resurrection and Angels). Accordingly, God has written down in the Preserved Tablet ("al-Lauḥ al-Maḥfūẓ") all that has happened and will happen. Thus Allah, Muslims believe, has measured out the span of every person's life, their lot of good or ill fortune, and the fruits of their efforts. 
Are we to understand from all this that we don't therefore have free will? Not at all: Muslims are keen to explain that it means simply that because God is timeless (literally outside of time) he already knows what will happen to all of us. It is in this sense only that our fate, or destiny, has been decided for us.
We can thus decide our own future, make decisions and pay the consequences - it's just that Allah already knows what we will do.
Really?
But what of the verses in the Qur'an that suggest otherwise? What of the verses that clearly tell us of Allah deciding our fate for us?
And if thy Lord willed, all who are in the earth would have believed together. Wouldst thou (Muhammad) compel men until they are believers? It is not for any soul to believe save by the permission of Allah. He hath set uncleanness upon those who have no sense. 10:100
Does not the above verse tell us we can only believe if Allah "decrees" it? And conversely it is He who decides who'll suffer "uncleanliness" (by which we are to understand unbelief)?
Lo! this is an Admonishment, that whosoever will may choose a way unto his Lord. Yet ye will not, unless Allah willeth. Lo! Allah is Knower, Wise 76:30
Aren't we being told two conflicting things here in the space of one verse? You can "choose" to follow the Lord ....but only if Allah "willeth". What happened to my free will all of a sudden?

Free will? Really?
God delights in telling us he guides those whom he wishes to, and equally sends astray those whom he (presumably) decides are worthless:
Whom Allah doth guide,- he is on the right path: whom He rejects from His guidance,- such are the persons who perish. Many are the Jinns and men we have made for Hell ...7:179
 The final line is chilling. Many are the men [...] we have made for hell. 

So here's a question that my convert friend has never answered:
What sort of beneficent deity creates beings to torture for an eternity? Presumably one with a wicked sense of humour, since he constantly refers to Himself as "the Most Merciful"...