Is it permissible to recite the Basmalah without vocalizing the last letter of each word with a kasra, and what is the ruling on reciting the word "الضالين" (ad-dalleen) in Surat Al-Fatihah with a shaddah on the lam or without it?

It is not permissible to pronounce the meem, haa, and noon in the Basmalah with a sukoon (vowelless) when connecting it [to what precedes or follows it], because this violates the consensus of the reciters who vocalize them with a kasra (i-vowel). This is a change in the vocalizations for which there is no narration. Similarly, the tashdeed (doubling) of the laam in "al-Dalleen" (the astray) is obligatory and must not be omitted. Whoever omits it intentionally, their prayer is invalidated, because the tashdeed in Al-Fatihah takes the place of two letters, and omitting it is like omitting a letter.