I will try to split your question into three parts and answer them separately.
Some general remarks: unlike in English dictionaries, it is rather uncommon for German dictionaries to provide any phonetic transcription. Most German words (more than 95%) are just read according to simple rules and you don't need a special IPA case for every word. Duden, one of the most comprehensive and known dictionaries of German language, provides IPA only for small amount of foreign words. But many dictionaries provide the audio of pronunciation, so you can use this if you are not sure how to read the word correctly.
Concerning a free web dictionary that would suit your needs I would recommend using the BeoLingus dictionary. It has the following traits:
- It provides you with extensive help on the words having many meanings in German, whereas for every word you usually get a derived German word that helps to understand the meaning (see first picture below).
- Every word in German it gives you an English translation (though you can also choose to use Spanish or Portuguese as well).
- Almost every word -- both in German and in other languages -- has pronunciation associated with it.
Here is a screenshot:
Down below you can easily navigate to word usages (example sentences), synonyms etc.
If you are looking for declination or word construction you can easily find them on related sites: just click on the word and you'll find all necessary direct links in the opened context menu:
If you can drop the English language from your criteria then you definitely should try Duden online. It is a monolingual dictionary (so, it is completely in German), but it provides all the information you need for understanding how to use certain German word:
- Grammar information (part of the speech, usage frequency, declination etc.)
- Synonyms and related words
- In case of foreign words it also provide IPA together with audio file, for genuine German words it gives only the audio
Here is an example:
From all offline one language dictionaries I tried I liked Wahrig most, which is available both as software (rather outdated, unfortunately) and a printed book. This is somewhat more than just a dictionary and more like an encyclopedia, but still it contains valuable information on every word including pronunciation, grammar remarks etc.
Of course, there are also the complete Duden series of dictionaries, many of those are available in electronic form as well. I especially recommend the Bildwörterbuch (picture dictionary), which exists now in two editions: one for language learners and one for mere Germans (so-called "Band 3"). It is really very entertaining and educative, but it does not relate to your question...