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We investigate the observational constraints on <inline-formula><mml:math><mml:mi>α</mml:mi></mml:math></inline-formula>-attractor inflationary models and their postinflationary reheating dynamics in light of the latest cosmic microwave background (CMB) data from ACT DR6 combined with Planck18, <inline-formula><mml:math><mml:mi>BICEP</mml:mi><mml:mo>/</mml:mo><mml:mi>K</mml:mi><mml:mi>e</mml:mi><mml:mi>c</mml:mi><mml:mi>k</mml:mi></mml:math></inline-formula> 2018, and DESI (collectively denoted P-ACT-LB-BK18). Focusing on both E- and T-type attractor potentials, we analyze how inflationary observables, namely the scalar spectral index <inline-formula><mml:math><mml:msub><mml:mi>n</mml:mi><mml:mi>s</mml:mi></mml:msub></mml:math></inline-formula> and the tensor-to-scalar ratio <inline-formula><mml:math><mml:mi>r</mml:mi></mml:math></inline-formula>, are indirectly influenced by reheating parameters such as the reheating temperature <inline-formula><mml:math><mml:msub><mml:mi>T</mml:mi><mml:mi>RH</mml:mi></mml:msub></mml:math></inline-formula>, the inflaton equation of state <inline-formula><mml:math><mml:msub><mml:mi>w</mml:mi><mml:mi>ϕ</mml:mi></mml:msub></mml:math></inline-formula>, and consequently the inflaton's couplings to Standard Model (SM) particles. We incorporate constraints from primordial gravitational wave (PGW) overproduction via <inline-formula><mml:math><mml:mi>∆</mml:mi><mml:msub><mml:mi>N</mml:mi><mml:mi>eff</mml:mi></mml:msub></mml:math></inline-formula> bounds, which are particularly relevant for stiff postinflationary dynamics. Additionally, we include theoretical constraints from Coleman-Weinberg (CW) one-loop radiative corrections, which impose an upper bound on the couplings, as well as inflaton self-resonance, a nonperturbative effect that can occur even in the absence of inflaton-SM interactions and imposes a strong lower limit, particularly significant for <inline-formula><mml:math><mml:mn>1</mml:mn><mml:mo>/</mml:mo><mml:mn>3</mml:mn><mml:mo>≲</mml:mo><mml:msub><mml:mi>w</mml:mi><mml:mi>ϕ</mml:mi></mml:msub><mml:mo>≲</mml:mo><mml:mn>0.7</mml:mn></mml:math></inline-formula>. Our analysis shows that E-models allow a broad range of reheating scenarios, including matter-like reheating (<inline-formula><mml:math><mml:msub><mml:mi>w</mml:mi><mml:mi>ϕ</mml:mi></mml:msub><mml:mo>=</mml:mo><mml:mn>0</mml:mn></mml:math></inline-formula>), whereas the T-model yields more restrictive results and remains viable only for <inline-formula><mml:math><mml:msub><mml:mi>w</mml:mi><mml:mi>ϕ</mml:mi></mml:msub><mml:mo>&gt;</mml:mo><mml:mn>1</mml:mn><mml:mo>/</mml:mo><mml:mn>2</mml:mn></mml:math></inline-formula> for all three nongravitational interaction channels, <inline-formula><mml:math><mml:mi>ϕ</mml:mi><mml:mo>→</mml:mo><mml:mover><mml:mi>f</mml:mi><mml:mo>̄</mml:mo></mml:mover><mml:mi>f</mml:mi></mml:math></inline-formula>, <inline-formula><mml:math><mml:mi>ϕ</mml:mi><mml:mo>→</mml:mo><mml:mi>b</mml:mi><mml:mi>b</mml:mi></mml:math></inline-formula>, and <inline-formula><mml:math><mml:mi>ϕ</mml:mi><mml:mi>ϕ</mml:mi><mml:mo>→</mml:mo><mml:mi>b</mml:mi><mml:mi>b</mml:mi></mml:math></inline-formula> are considered. For stiffer equations of state, an intermediate coupling window survives, bounded from above by CW corrections or <inline-formula><mml:math><mml:mn>2</mml:mn><mml:mi>σ</mml:mi></mml:math></inline-formula> observational limits, and from below by the combined PGW and self-resonance constraints. We derive updated bounds on inflaton couplings for both decay and scattering channels and identify parameter regions consistent with successful perturbative reheating. These results establish a robust connection between inflationary dynamics, reheating physics, and particle interactions, and provide concrete targets for upcoming precision CMB observations.