IAD and IAH international connection times

Hi everyone, can some please help me? I am supposed to book 2 tickets to LHR tonight for travel in August. One is from TPA, the other ONT. Looking at them again today, they both seem to have rather tight connection times, are these doable?

6:55 p.m.
Tampa/St. Petersburg, FL (TPA) 9:10 p.m.
Washington, DC (IAD - Dulles) Flight Time:
2 hr 15 mn UA314 | Airbus A320


Change Planes. Connect time in Washington, DC (IAD - Dulles) is 40 mn.

9:50 p.m.
Washington, DC (IAD - Dulles) 10:15 a.m.
London, England (LHR - Heathrow)
Departing Arriving Duration Flight Information

11:35 a.m.
Ontario, CA (ONT) 4:43 p.m.
Houston, TX (IAH - Intercontinental) Flight Time:
3 hr 8 mn UA5164 | Canadair Regional Jet 700


Change Planes. Connect time in Houston, TX (IAH - Intercontinental) is 1 hr 22 mn.

6:05 p.m.
Houston, TX (IAH - Intercontinental) 9:40 a.m.
London, England (LHR - Heathrow) Flight Time:
9 hr 35 mn

UA985 | Boeing 767-300

While I have flown direct international (simple jaunt down to Cabo from SNA), I have never flown with connecting flights and am unsure of the protocol. I have looked thru the forums and other places online, but still am worried.

This is my first time posting (been lurking for awhile), I’m sorry if I don’t have the right forum or format.

Any help would be greatly appreciated!!