Assuming you're on time into DFW then 1hr 35 should be ample time. My last couple of trips into the US have both been via DFW and immigration / customs was a breeze. If you have GE then the kiosks are still there. However, all of the other passport kiosks have been removed. On my last two trips there was no queue and I was through in seconds. Interestingly, no stamp in my passport on either occasion (although as a permanent resident that may be the new norm - it may be different for visitors).
As has been said above the CBP officer you speak with handles both immigration and customs. I was asked if I had anything to declare. It goes without saying but it's best to give a full and frank disclosure here. On my second trip I had nothing, but on the first trip we had a wedding gift, some clothes, a couple of vinyl albums, and a couple of bags of crisps from the BA lounge in LHR for our daughter. The reason I say this is because on a previous trip we brought back more than our combined allowances (which we fully declared on the blue form) and so got sent to secondary. The CBP agent totted up what we'd spent, subtracted our combined $1600 allowance, and told us we owed $6 in duty - but that because we'd made a full and complete disclosure and had all the receipts etc. she wasn't going to charge us. You only have to watch any of the "Border Protection" type of documentaries to know what happens when you're not truthful
After you clear immigration / customs it's down the escalators into the baggage claim hall and then out into the international arrivals area. If you need to re-check bags the AA desks are over to your left. The AA agent will tag your bags and then you need to wheel / carry them over to a couple of handling agents who will load them onto a conveyor. Easy peasy.
Then it's the escalator up to departures and through TSA. If you are standing looking at the AA desks at the transfer area the escalator is behind you, over your left shoulder. The prominent sign is for the Hyatt hotel but that's the escalator you need. TSA is at the top of the escalator. Pre-check may or may not be available depending on the time. However, on both my last trips it took longer to walk along the snaking tensa barriers to TSA than it did to get through security itself.
Once you have cleared security you're back in the D gates area. If your flight isn't departing from the D gates than you need to take the AirTrain to your respective terminal. Each terminal has two stops and everything is well signposted in terms of which train to get, and where to get off.