Security Strategy For Sensitive Data

I am working towards launching a site that, among other things, will be a repository for sensitive data on war crimes. As these crimes are ongoing, and occur in a location where assassinations are endemic, I need to develop a comprehensive security strategy that takes into account all levels of the interface between end user / witness and the site / database itself.

I have considered, but am open to insight and advice on, the following:

1. Data security laws in given countries, in order to ensure the privacy and integrity, as much as possible and away from political / state interference, of data communications. Concerns include the interception of data in transfer and the security of stored data (the United States and the UK are almost certainly cancelled out in this regard. Canada appears significantly better, though Greece, it appears, has the greatest level of legislative protection).

2. Encryption as a technique to ensure the security of transfered and stored data. I am particularly interested in best practice advice on encryption.

3. Javascript as a means to establish a more secure interface between the end user (i.e., the browser interface) and the secured database into which sensitive data will be inputed. Has anyone used this, or other techniques of overcoming the inherent insecurity of the browser interface?

4. Various best practices concerning php, MySQL and Apache security. Any and all advice, or guidelines, welcome.

5. Considerations relative to dedicated hosting, and also colocation hosting as an option.

In general, my problem is to ensure that the identities of witnesses, so much as is technically conceivable, can be protected from extra-judicial interference or surveillance. Nothing about this site will be illegal in any way. The problem is that the witness testimony will be about the actions of a powerful state that has demonstrated its disrespect for law.

Ideally I'd find in these forums a few individuals with whom I could discuss these technical matters off-forum. At the same time, general responses would be values.

The site that I'm building is non-profit (indeed zero budget) and does not represent any political party. It's a people's initiative, against aggressive violence and in support of international law.