bev, with your old TV and only a coax input, you're at a distinct disadvantage with a DVDR.
On the Ch. 6 thing, it can't be anything with the 3575 since the coax In/Out of the 3575 is just a pass-thru of whatever comes in on the antenna coax...you aren't seeing anything from the 3575's tuner or disc drives (HDD or DVD).
To see anything produced by or thru the 3575, you have to have a line connection from one of the 3575's line outputs to a line input on the TV. But, without a line connection on your TV, you'll have to use your VCR as the "conduit" to see the 3575's channels or shows recorded on the 3575's HDD or played on a DVD.
More complicated, but you should be able to connect the coax from antenna to the 3575, then continue the coax from the 3575 coax Out on to the VCR, then on to the TV. That will allow you to watch TV normally w/o turning the 3575 or VCR on (the VCR should also be a coax pass-thru)...whatever your antenna can receive will be passed thru the 3575 and VCR to the TV.
To then see channels from the 3575's tuner or shows on the 3575 HDD or DVD, connect a line output from the 3575 (yellow, red, white) to a line input on the VCR. When you want to watch something from the 3575 itself, you'll have to turn the VCR on and select the VCR line input you connected the 3575 to (L1, L2, etc.), which will allow the 3575 signal to continue on to the TV when you press the TY/VCR button. (If/when you get a newer TV with Line Inputs, just remove the VCR and connect directly to the TV...and your life will be simpler.)
Make sure you go to SETUP > Channel > Auto Channel Preset-Antenna once you have the 3575 connected to the antenna coax in to see what channels the 3575 can pick up.