Do you mean very slow by your general, working-world standards, or the standards you would expect from them given other signals (verbal fluency/evidence of understanding, education level)?

If the latter, it could well be perfectionism getting in the way (shoddy existing work doesn't discount this possibility). Encourage 'iterated failures at any old sub-problem' perhaps? It's the only way I know how to deal with all three of those problems myself.

When I was starting out with small-ish programs, IDEs gave me performance anxiety. So I'd write in bits and pieces in Evernote or notepad, converting plain descriptions into code, and only merge it all into a single file ready for execution right at the end.