By DAVID GONZALEZ (NYT)
Cuba’s leading dissident Oswaldo Paya faults his government for manipulating fears of invasion by United States to justify its harsh line on opposition; Paya is leader of Varela Project petition drive seeking personal and political freedoms; majority of 75 dissidents arrested in Apr are Varela Project activists; Paya says they are being kept in prison under inhumane conditions far from their families; says he welcomes American moral support, but rejects any financing from United States; emphasizes that any resolution to Cuba’s political situation must be peaceful and homegrown (M)