After the most recent US instructions, are there any prohibitions against transporting spare lithium ion/metal batteries in the cabin?
Short answer: Yes.
Slightly longer answer: IATA changed the regulations within the 58th Edition of the Dangerous Goods Guidelines, effective January 1st, 2017. For passenger aircraft, lithium batteries are only allowed if they are installed in equipment. Standalone lithium ion cells or batteries are no longer permitted on passenger aircraft.
If you want to air freight lithium batteries: Air transport of Lithium batteries is only allowed if they are charged to 30% or less of their nominal capacity. Also, the cell must comply with the United Nations (UN) Manual of Tests and Criteria, Part III, Sub‐Section 38.3 (see page 394ff in this document) and proper packaging and documentation must be ensured.
The rules in the US and elsewhere differ slightly. From this Energizer document on US air freight:


Batteries must be of a type proven to meet the requirements of each test in the UN Manual of Tests and Criteria.

Batteries must be packed in strong outer packaging and be packaged in a manner to prevent short circuits and separated so that electrically active terminals cannot come into contact with each other.

The gross weight of the shippable container shall not exceed 30 kg. 

For lithium‐ion cell, the equivalent lithium content is not more than 1.5 g; or lithium‐ion battery, the aggregate equivalent lithium content is not more than 8 g.

The shippable container must be capable of passing a 1.2 m. drop test in any orientation without spillage of the contents of the packaging, damage to the batteries inside or shifting of the contents that could lead to short circuit.

The shippable container must be marked to indicate lithium batteries are present and that special procedures should be followed if the package is damaged.