Gandalve?

[Majestic]

The pronunciation of æ is nowhere described that I'm aware of. A sounds like a in father, not a in apple. Since Gandalf obviously isn't supposed to sound like Gondolve, I think it's a safe bet that mannish and hobbitish words are generally pronounced as they would be in English, and not according to the pronunciation guide for other, ancient languages.

Of course, even just saying "pronounced as they would be in English" has an absolutely massive amount of variety. In the U.K. there's quite a variety in the way words are pronounced (shoot, even just in England alone), and then those same words sometimes are pronounced incredibly different over here in the U.S. (and the different dialects and accents here also have a ton of variety).

[Stormcrow]

In general, when referring to English in Tolkien, understand it as Received Pronunciation.