No.

That's why I advise not to use DB code (or code using developer's keys or similar) in applets...
The preferred option is to make the applet to communicate with server side scripts, so no sensible data go over the wire.

You cannot stop the users from downloading the file: the browser has to have it on the client side to run the Java code!
You might encrypt the strings, then decode them on the fly, but if the code can be decompiled, it can be used to decode the strings... There are obfuscators, but all they do is to make harder to read the decompiled code. It can be still reused/understood, with patience.
Self-made security measures are prone to be easily defeated... Some people might be more motivated by the challenge than by the goal (to access your data and play with it). Although beyond the usual play (like changing the content of a Web site, just for fun), we see more and more criminal usage of stolen data (credit card data, or even just reselling lists of e-mails).

As phi.lho said, you have to put your sensitive parts into the PHP code which is executed server side, i.e. the 

It is hard to make such application 100% secure, I fear...
Don't take my remarks as real security advices, as I don't have knowledge/experience in the field, it might be better to find advices from people having really implemented something for real games...

But well, thinking out loudly, I think the server should generate an id for the player. It passes the id to the applet, that provides it back on each request, which is checked on the server. Thus, you eliminate at least the simplest tinkering, as one has to identify itself on the server to make updates like changing the high score of this user. Now, one can sniff the id and use it. It can be encrypted in some way, but again, the decrypting part can be decompiled and analyzed. Perhaps using SSL can help in the secure part, I don't know. But this is becoming quite complex...
It can be interesting to see who OAuth (used by Twitter) works, too.

I see. Then your pass parameter makes no sense at all. Just remove it, it won't help.

Just set up your web server to support HTTPS. I wouldn't worry about slowdown, given that you just transfer a few bytes of data.

Except you use noLoop() ...