A What are the different types of long-lived hadrons and their properties?

[snorkack]

Classically yes.
You also have to care about the strong force, you can not treat the pions in pionium as two "heavy" electrons/positrons
this is a nice overview https://arxiv.org/abs/0711.3522v2

Page 4 (Chapter 1 Introduction):

The distance rB ≃ 220 fm is much smaller than the
hydrogen radius, but still much larger than the range of strong interactions, which
is typically of the order of a few fm. It is for this reason that strong interactions
do not change the structure of the bound–state spectrum in a profound manner.
At leading order in an expansion in α, the energy of S-wave states of pionic
hydrogen is still given by the standard quantum–mechanical formula

This
corresponds to a lifetime τ1 ∼ 10−15 s, which is much smaller than the lifetime of
the charged pion, τπ ∼ 10−8 s, so that the pion in the atom can be considered a
practically stable particle. Despite of its short lifetime, pionic hydrogen can be
considered a quasi-stable bound state, since the pion travels many times around
the proton before decaying, as the ratio 1
2 μcα2/Γ1 ∼ 10³ indicates.

I had a general impression to that effect, but thanks for providing authoritative confirmation to my opinion.
So, a tetraquark, pentaquark or hexaquark is characterized by strong interaction as perturbation to electromagnetics - strong decay paths if they exist (but leptonic atoms may also decay by lepton capture, even though this is weak rather than strong) and strong interaction energy level shifts.
The review discusses pentaquarks π^-p and Kp.
Obviously all longlived negative diquarks would be prone to forming such pentaquarks, because their Bohr timescale is 10^-18 s or less, but their free lifetime exceeds 10^-13 s. This means that we also have
3) D^-p
4) D_s^-p
5) B^-p
6) B_c^-p
What are their strong energy shifts and decay widths?
I note something about D_s^-p...
D_s^- is not charming because it is anticharming. Therefore, it cannot possibly react to form a charming baryon. The quark is the strange one.
But look at the masses:
D_s^- 1968,3 MeV
D⁰ 1864,8 MeV
p 938,3 MeV
Λ⁰ 1115,7 MeV
so: D_s^-+p=2906,6 MeV
D⁰+Λ⁰=2980,5 MeV
Cannot see a strong decay for D_s^-p.

 

[malawi_glenn]

You also have to care about the strong force you can not treat the pions in pionium as two "heavy" electrons/positrons

I should have written "the symmetries of the strong interaction"