Worry not about Iseki engines. They have been around a very long time, one of the original Japanese manufacturers, and the 20+ year old Iseki engine in my MF runs flawlessly, though cold hearted, likes lots of glow plug before starting.
I believe Iseki supplies most of the engines for Massey Ferguson under 100hp.
Unless you are going to leave the backhoe off and operate mostly without it, I'd suggest you consider renting a mini excavator or trencher when you need it. Backhoes add a lot of weight and length to a machine and are often difficult to install. I considered one and then realized that cost would rent a lot of very fancy small excavators that would work better and still keep
lots of money in the bank. I think most backhoes should be avoided when they are only nice to haves, plus digging in the ground and hitting very expensive things is sometimes best left to the experts. Having said that, as an extra tractor, yeah a TLB would be great to have around. My ditches would never be so nice...
grapples and implements can be bought anywhere. Likely you'll get a better grapple for less money at Everything Attachments.
Good luck and have fun with this.
Get some seat time, make sure the ergonomics really work for you.