If you are beaconing only, set the squelch pretty high. You don't care if you hear fringe stations and repeaters will have the signal strength to open your radio. Really you just don't want to step on close-in stations, so I go mid range or higher. If you are tracking other people in simplex, then you'd need to take more care in squelch.
Depends on propagation and range, you might have a better aspect to the Parker repeater. Could also be the Lakewood repeater was busy with other traffic and your packet was stomped on. I wouldn't worry too much which digipeater hears you as long as you are less than 2 hops to an I-GATE and you get at least 50% of your packets digipeated. Some days you'll get almost 100%, others not. If you are getting a lot of dropped packets, then start worrying.
With a mic/speaker interface you do need to be a little more careful setting levels and should listen to your TX on a second radio. RX is a little tougher. Turn it up until the TT looks to be decoding reliably I guess.
"Silent enim leges inter arma." -- Cicero