"Lent" is indeed a word. It is the past participle of "lend".

Definition
lent (LEND)
past simple and past participle of lend

eg I lent her my handkerchief.

Learnt is the past simple and past participle of learn.

eg He learnt his lesson.

"Learned" is defined thus:
learned
adjective FORMAL
describes someone who has studied for a long time and has a lot of knowledge:

eg a learned professor

From Cambridge Advanced Learner's Dictionary.

The other words you cited fall into the same category. Americans attempt to distort the language but for reference you should always consult an English, English dictionary if you are going to complain about the use of allegedly, non-existent words. Especially as this topic is about the English not the Americans.

The FULL rule, as I learnt it, is:

"'i' before 'e' except after 'c' when it rhymes with 'me'."

I have yet to find any exception to this rule. The reason for the failure is the problem that many people did not learn the full version of the rule and many teachers were ignorant of the full version.

I was taught the full rule by my Mother who was a licensed Teacher with many years experience and I myself am a Trained Primary School teacher.

When I was in the Fourth Grade of my primary school I pointed out the full rule to the teacher who had never heard it before. She then tried to list may of te words that did not follow the shortened rule and became very upset, and almost abusive, when I pointed out that none of her extensive list rhymed with 'me'.