The pics aren't clear on this question, but do you have easy enough room to replace the entire drain assembly with a new drain kit? Fifteen bucks plus ABS cement. They're very easy, very forgiving, and don't corrode with drain chemicals.

I think that pipe is brass. Grounding to plastic is not possible.
Given your inexperience with plumbing, it is time to call a pro.

Faster abd easier to replace everything in picture. The replacment for the busted pipe screws into new overflow and will have to be hacksawed to leigth. Even if you torched off the old one and soldered in a replacment,those other parts will rot out soon. If looking down into tub drain you see a metal X,you might buy a cheap "shoe wrench" while picking up parts.

I'm definitely not a pro but I just need some guidance. I can't afford a plumber, period.
I know I can't ground to plastic (really?), I didn't know it was plastic until i tightened down on the bracket, who would have thought it was plastic, seeing that everything else is brass, galvanized metal, etc..
So my problem as I see it is, unscrewing the tub drain shoe, the wood will get in the way, at least it appears, which begs the question...how did they get it on there, it must have been installed on the tub before the tub was lowered into place? And I cannot unscrew the fitting at each end of the busted plastic pipe, it is seized. If I could get a rubber hub connector over the tub drain shoe, I think that might be the easier fix...but then I still need to get that fitting at the other end to break free. Any suggestions?

I thought drawing on the pic would help.
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The red arrow points to the drain shoe, correct? The blue arrow points to a fitting that should unscrew, correct? The yellow arrow points to the fitting that is seized. Basically, if I can get both fittings that the blue and yellow arrows point to, I am good, correct?Then just replace these pieces with something of the same type.
What are my options if I can't get the two fittings to budge? It appears to me if I have to unscrew the tub shoe I will have to remove some wood to have room to do that.

Let me say that what you are lacking in plumbing skills is more than offset by your green thumb,apples in piticular. I can't even keep the trees from dieing,much less produce apples.
To me it appears the busted pipe is brass and is soldered to the shoe. If it is screwed in,it's without a doubt brass. Normally the drain part visiable inside tub screws into and secures the shoe. Shoe doesn't need to rotate,just held while other side is unscrewed from inside tub. If you get to that point,the rest is easy so replace everything. If the busted pipe is screwed in rather than soldered,it's a matter of picking it apart and cleaning threads with a small wire brush before screwing new pipe in. Heat from a propane torch and two pipe wrenches may be nessary to break the yellow arrow nut loose. The tee must be held in place while nut is being unscrewed.
But again,if you get busted pipe out of shoe at blue arrow,it's easier to remove overflow than mess with the seized nut.

It also looks as if excess amounts of drain cleaners have been used on that tub. For my part, those are not necessary on tub drains at all. We do not use them at all at our house. The "drain cleaners" sold to consumers are mostly ineffective. But they do enrich those who make and sell them.

i just made my second trip to lowes to get the right tool to remove the tub shoe. i was given the tool on the right at first but, it is too big. it won't go down far enough to engage that cross piece down inside. the tool on the left isn't the right one but it looked like it might work, i threw a hail mary. so any ideas on how to remove it without leaving the house again? i have a lot of tools.
i did buy the whole waste and overflow unit, just trying to remove the old shoe first.
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"i threw a hail mary. so any ideas on how to remove it without leaving the house again?"

Not realy but I have four facts you might consider. #1 Plumbing tests ALL DIYERS. #2 Once you start with the shoe wrench there is no turning back and no Guarantee you will not bust it before you unscrew it. #3 It's best to always have a plan B before you start. #4 Plumbers are accustomed to seeing failed attempts when the get to a job. If he's a gentleman he won't laugh out loud but the shaking belly usualy gives them away.
Plan B in this case is a saw and/or hammer and chisel. More than once I have cut through threads on each side and wacked it with a chisel before trying to unscrew it.

klem, well i'm not sure which plan I took, but I got the old one out. Vise grips on a pair of lineman's pliers broke it free, then i had to get under the house and hold the shoe while my wife turned it from in the tub. she humored me just fine. my "catastrophe" cost $36 to repair (after i return the shoe wrench that didn't fit). a plastic waste overflow kit and some plumbers putty and a couple hours piddling on these forums and youtube cost some plumber a visit to my house.

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now if you want to talk apple trees i can probably help you ;)

After the fact, but replaced my brass tub drain a short time ago and loosened the drain flange by going around the inside with a cold chisel. Got it to screw out with a few whacks but believe the shock of the mild hammer blows helped a lot.

Looks great thomis,I'm glad to hear you didn't let it wup you. The experience gained will serve you well into the future and you should take comfort in knowing that a tub drain is the most difficult one in the house. Now take your helper out for dinner and spend part of the $300 you saved.