Diagnosis: stage 1 or t1 squamous cell carcinoma, just below glans on penis underside. What is percentage chance it has spread to lymph or elsewhere?

Really. This is really something your doctor should discuss with you.
Depends. Stage i means no lymph node spread or in tna classification t1 in t1a no lymph vascular invasion in t1b into sub endothelial connective tissue with lympho vascular invasion n 0 is no lymph nodes m 0 (zero) no distant metastasis. In general early stage t-1 will have minimum chance of metastasis , and curable.( of course need work up and staging ).