P.M.
Why are you unable to sternly, quickly and forcefully tell him simply to "STOP IT NOW!" ? If that doesn't work, then a quick slap to the butt. Not hard, not to cause pain or a red mark, but enough to startle him to stop the behavior that is inappropriate.
All the love and logic will not help discipline a child if they see no actual consequence for their actions... which time outs and talking to them (especially this young) does not work with most children.
***ADDED after 4 flowers***
My daughter has been spanked on occasion since she was 18 months old. She stills loves me - to the point where I sometimes get frustrated with how many hugs, kisses and "I love yous" I get in a day. My daughter trusts me completely, because when I say something (whether positive or negative) I mean what I say and I follow thru. I keep my promises as well as my discipline expectations.
She is almost 6 y/o now and all I have to do is start counting down from 5 (5,4,3,2,1) by the 3rd warning because she knows then it will end in a spanking for her inappropriate behavior. Needless to say, she tends to behave appropriately and is a very well rounded and well liked child.