Integer custom fields with select/radio controls - multiple issues

1. Importing field labels to integer custom fields raises a validation error.
When importing into custom field that uses a radio/select control, one should be able to import both keys and values (see
https://book.civicrm.org/user/current/common-workflows/importing-data/ - "your data source can use either the label [...] or value")

This does work when importing labels into a field defined with alphanumeric storage. However, when the field uses integer storage, the labels are validated against the integer (timestamp) field type, and a fatal error is raised:
One of parameters (value: Yes) is not of the type Timestamp

I'm attaching the backtrace. After fixing this for integer fields, it may be worth testing this behaviour against Yes/No fields as well.

2. Searching by integer fields with key-value maps yields no results
However, searching in fields with alphanumeric storage does work

3. Exporting integer fields with key-value maps results in a integer key values being exported

4. related - alphanumeric field with key-value maps (1=>"I would like to receive mailings"), fields are truncated to the database field length on export. So, if I set a field length of 5, when exporting I get "I woul" in the CSV. The problem might also apply to integer fields once #3 is solved.