Do any English words end in /ɒ/, a short o?

In general, English words do not end with any of the stressed "short" vowel sounds (/ɒ/, /æ/, /ɛ/, /ʌ/, /ɪ/, /ʊ/). This is not an absolutely exceptionless rule: interjections may not follow it (for example, I have /æ/ in "yeah" and /ʌ/ in "duh"), and I don't find it particularly difficult to pronounce nonsense words ending in stressed /ɪ/, for example.

In American English, historical "short o" has been merged into the originally "long" vowel sound /ɑ/, so the original restriction on the distribution of the "short o" sound no longer applies, at least not on the surface level (the word spa ends in the same sound /ɑ/ that is used for the "short o" sound in pod, so pod and "spa'd" rhyme).

Furthermore, as far as I know there is no dialect of English where the sound /ɒ/ is in common use in fully unstressed open syllables. (Unlike /ɪ/ and /ʊ/, which some accents use in words like ready or gradual.)

So I don't think you'll be able to find any word ending in /ɒ/.

The symbol /ɔ/ is most commonly used in transcriptions of English to represent a vowel sound distinct from the sound of "short o". It is also transcribed /ɔː/ (with the IPA length marker "ː") in the context of British English to indicate that it functions as a "long vowel" in the British English vowel system. This vowel sound does occur word-finally, in various words spelled with -aw (law, claw, raw, straw), and in "non-rhotic" accents also in words spelled with -oar, -ore such as roar, more, tore, bore (and some words spelled with -oor such as door and floor).

The British English /ɒ/ phoneme ("short o") may be realized as the IPA phonetic vowel [ɔ], and the British English /ɔː/ phoneme may be realized as the IPA phonetic vowel [oː], but purely phonetic transcriptions are not very commonly encountered, particularly not when discussing restrictions on the distribution of sounds in a language's sound system. (Contrariwise, in American English the phoneme transcribed /ɔ/ may be realized phonetically as something like [ɒ]—even in accents where it is not merged with the open unrounded /ɑ/ sound, it often is relatively close to it phonetically.) This mainly comes up as an issue when people are trying to compare vowel sounds between different languages: for example, comparing English "o" sounds to those of Italian, French, or German.

Yes, a few do, but not very many. Common examples are saw, law, claw, draw, flaw, jaw, raw, thaw, or a crow’s caw.

This is because for the most part, /ɔ/ patterns like a “checked” vowel (meaning a lax vowel like the ones that also prototypically occur in DRESS, KIT, HAM, PUT) in that it doesn’t like to end a syllable without a consonant or glide following it. So words like soft and loft and coughed, or sawyer and lawyer, are more likely than just plain saw and law type words.

Normally a word-final tense vowel like phonemic /o/ that isn’t reduced will take a terminal glide phonetically, so an extra /w/ and sometimes written phonetically as [oʊ].

Sometimes words spelled with ‹a› are pronounced /ɔ/, as in one regional pronunciation of the stressed syllable in the city of Chicago [ʃɨ ˈkʰɔ goʷ], or even grandma in the eye-dialect spelling of grandmaw.

This ends up being reflected in spellings like fellow. Notice though how when that gets reduced in the unstressed position, it gets spelled fella, reflecting that it has become an open back unrounded /ɑ/, phonetically reduced further even to schwa.

The other kind of reduction we see in words adapted into English from other languages where they had originally ended in /o/ is for them to go to /u/. This happens in words like buckaroo from Spanish vaquero or vindaloo probably from Portuguese vin(ho) d’alho, or even in lasso from Spanish lazo but pronounced /ˈlæsu/ with /u/ in English rather than /ˈlɑso/ as though it were Spanish.