From what I can gather from the fourth Catilinarian and Sallust is that there were three proposals that day.

First, Dec. Silanus´ death penalty (which later changed to the "ultimate penalty, heh).

Second, C. Caesar, imprisoment for life without a right to a trial or an appeal. I think there´ve been some scholars who - quite understandably - have thought that this was temporary but atleast the Handford translation I have is unequivocal about it.

Third, C. Cato, death penalty. This proposal is in Sallust (too lazy, can´t find the energy to type it).

Cicero didn´t propose anything, his fourth Catilinarian is about: 1) he has given the matter to the senate though he could have carried the execution on by himself 2) though this could entail personal danger to himself later he would carry out the decree of the senate 3) he did not say which option he preferred though you can read it in the argument.

As for guilt, the senate later passed a decree which said that anyh future attempts to charge Cicero would be treasonable. Yes, this did not stop Clodius who had the backing of Pompeius, Crassus, and Caesar.