Hi,
I`m going to my 8th job, so I have some experience in lots of companies.
Concerning your first question , the answer is Yes. I mean , everytime you have a legally dispatchable MEL item , you are expected to go.
In the example you gave , if you lose one engine or one GEN you can at your discretion land in one of your enroute alternates.It`s cheaper than cancel or delay one flight because of a dispatchable MEL item.
About your second question....It`s fashion nowadays to monitor the block fuel.
There are 4 types of companies:
1. Up to the Capt.
2.They just monitor what do you refuel
3.They ask you to justify in the FPLN if you add fuel over a certain amount.
4.They don`t allow at all. (Qatar airways)
I have a simple way to solve this. When the destination and alternates are marginal , I simply add he fuel I consider good and end of question.
If the destination is marginal and I the alternates are good , I refuel for what they want and I don`t even allow the comerciality to cross my mind in case I need to divert. Hapened of don`t even start the approach for my destination. Direct to alternate.
No big deal.
Just divert and go to the hotel. This is the way of dealing with modern pseudo smart big counters.
Cheers