How can I convert codon coordinates to genomic position?
HFE|LOC108783645 is https://www.ncbi.nlm.nih.gov/gene/108783645. You can use biomaRt to go from the LOCxxxx ID to location. Searching by HFE will give you a different location though, so you might have to account for such eventualities. It is a long and often manually intensive process.
You should be able to use entrez-direct/eutils to go from rsID to position
Unless there's some sort of natural language processing API, codon 109 of exon 3 of beta globin gene cannot be parsed by existing APIs (Unless it's always codon X of exon Y of Z, in which case you could use grep too get the components. Even so, going from exon + codon + codon base change to exact base location will require a lot of wrangling.